Coldcard entropy flaw shatters single vendor Bitcoin custody
Aug 4, 2026Tuesday, August 4, 2026Summary from 9 contributing podcasts.
- A five-year Coldcard firmware bug forced predictable wallet seeds, exposing over $70 million in Bitcoin to automated theft.
- Attackers are monitoring the mempool to hijack rescue transactions and retroactive CoinJoin mixing histories.
- Prominent Bitcoin advocates now mandate multi-vendor setups, abandoning single-manufacturer hardware reliance.
Self-custody logic broke this week. A five-year-old firmware flaw in Coldcard hardware wallets did not just compromise individual private keys. It triggered a cascading crisis across transaction mempools, CoinJoin privacy pools, and the fundamental rules of Bitcoin storage.
The vulnerability stems from a 2021 code rewrite by manufacturer CoinKite. According to Zach from Foundation on Ungovernable Misfits, CoinKite stripped GPL-licensed Trezor libraries to prevent competitors from copying its software, replacing them with proprietary logic. That pivot introduced a preprocessor macro error in C code that silently disabled the hardware random number generator. Instead of true randomness, devices generated seeds using a weak software fallback called Yasmarang or squeezed entropy into a narrow 32-bit window. A standard GPU farm can brute-force 32 bits of entropy in seconds.
The math failed silently for half a decade until July 2026, when researchers at Block publicly detailed how Mk2, Mk3, Mk4, and Q models produced deterministic wallet keys. The fallout was immediate. On Stacker News Live, hosts Keon and Grant reported that coordinated automated sweeps drained over 1,000 BTC, valued at roughly $70 million, within days of the discovery. Users who generated seeds after March 2021 without adding 100 physical dice rolls or custom passphrases found their vaults unlocked on the public ledger.
Moving funds off compromised hardware created a secondary tactical crisis. On What Bitcoin Did, host Danny Knowles and guest Rob Hamilton explained that automated exploit bots are actively monitoring the public mempool for transactions originating from vulnerable addresses. When an affected user broadcasts a transfer, attackers instantly compute the corresponding private key and submit a competing Replace-By-Fee transaction with higher fees to steal the funds in transit. To bypass these mempool snipers, migrating users are being forced to route transactions directly to miners through private submission pipelines like Mara Slipstream.
The contagion extends beyond active balances into historical transaction privacy. On Stacker News Live, Keon detailed how attackers holding the master list of compromised Coldcard seeds are systematically de-anonymizing past CoinJoin mixing rounds on platforms like Wasabi and Whirlpool. By identifying every weak key in a historical mixing pool, attackers strip away the mathematical obscurity protecting non-vulnerable participants. A hardware failure from five years ago is retroactively unmasking the financial histories of clean wallets.
Artificial intelligence radically accelerated this exploit cycle. On TFTC, James O'Beirne noted that while Western AI platforms like ChatGPT and Claude blocked requests to analyze the firmware for exploits, uncensored models like China's Kimi K3 mapped the exact logic errors instantly. Black-hat operators used these models to automate search scripts faster than human security teams could coordinate patch deployments. As guest Max observed on Presidio Bitcoin Jam, security teams must now assume hostile machine intelligence is scanning every line of published open-source code in real time.
This operational failure has permanently fractured the Bitcoiner consensus around single-vendor custody. On Citadel Dispatch and Rabbit Hole Recap, longtime advocates Matt Odell and Marty Bent publicly abandoned their multi-year endorsement of single-device Coldcard setups. They argued that relying on any single manufacturer's firmware - no matter how respected - creates an unacceptable single point of failure. The new baseline for high-value custody requires multi-vendor multisig setups using hardware from different vendors running independent codebases.
On TFTC, O'Beirne argued that hardware perfection is a dead end, urging developers to accelerate protocol-level defenses like covenants and time-locked vaults to prevent instant drain attacks. Meanwhile, on Presidio Bitcoin Jam, host Steve suggested that high-net-worth holders will increasingly split assets between self-custody and regulated custodians like River to build circuit breakers against hardware zero-days. The era of blind faith in hardware wallets is over.
Source Intelligence
- Deep dive into what was said in the episodes
SNL #235: The most important photo of my life • Aug 3
- On July 29th, a critical vulnerability in Coldcard's firmware led to many users' Bitcoin being swept, stemming from a bug that prevented the hardware's random number generator (RNG) from being used for seed generation.
- The Coldcard bug, present for five years, affected MK3, MK2 (with updated firmware), MK4, MK5, and Q models, enabling an attacker to steal nearly 1,000 coins, totaling $70 million, within 24 hours.
- The attacker's actions were deemed "amateur" by experts, as they consolidated funds immediately, reused addresses, and paid high fees (80 sats per vbyte), making the attack easier to trace.
- Bitcoin seeds typically require 128 or 256 bits of entropy; however, the vulnerable Coldcard MK3 only provided 32 bits, while MK4, MK5, and Q models had 70 bits, significantly lowering security.
- Keon anticipates hundreds of millions of dollars in further thefts, as the initial attack targeted low-hanging fruit (MK3) and subsequent attackers using AI tools like "Kimi" could exploit other vulnerable models or remaining UTXOs.
- Coldcard users should immediately move funds to a new, securely generated seed, ideally using a hot wallet or an exchange for safety, or direct to miner transactions to avoid mempool snipers.
- Justin Shocknet suggested that the Coldcard vulnerability could reduce the anonymity set of CoinJoin rounds for affected users, as attackers with compromised seeds could de-anonymize their transaction history.
- Jason B, a jazz musician and aspiring Bitcoiner, draws parallels between Bitcoin and jazz, both lacking a central "ruler" or fixed canon, aligning with his preference for systems without needless control.
Also from this episode: (3)
Politics (1)
- Keon met a hacker named Rob who claims responsibility for Russiagate and operates Ford Intelligence, a newsletter selling intelligence to CEOs, heads of state, and private security, pitching it as "Palantir for civilians."
Coding (1)
- The bug was a subtle misinterpretation of a C preprocessor macro, `ifndef`, meaning "is this symbol defined" instead of "is this symbol zero," leading to the use of low-entropy code.
Society (1)
- Malos10, a photographer from Venezuela, shared a photo of a pregnancy test, announcing the upcoming birth of his child, which he described as the "most important photo of my life."
Not Cold Enough | Bitcoin News • Aug 3
Also from this episode: (9)
Other (9)
- David Bennett states Coldcard models Mark III, Mark IV, Mark V, and Q with firmware 4.x+ were compromised by a predictable seed generation vulnerability, while firmware 3.x models appear unaffected. The flaw, active since 2021, stemmed from a software error that reduced entropy from 2^256 to approximately 2^32 bits, making wallet seeds easily guessable.
- Bitcoin began moving from affected Coldcard addresses around July 30th, 2026, via coordinated, automated sweeps targeting large balances first (over 1.15 BTC), then smaller amounts in subsequent waves. Attackers could generate candidate seeds and compare them to the public blockchain without direct access to devices.
- CoinKite initially dismissed public warnings, continued to sell affected products for 48 hours after the vulnerability was known, and later released a firmware update that reportedly bricked devices. David Bennett argues CoinKite's failure is inexcusable and recommends never using their products again, including OpenDimes and BlockClocks.
- Volunteer teams, including BTC Sessions and Rob Hamilton, provided extensive support to affected users, with BTC Sessions reporting efforts protected "tens of millions of dollars." Foundation Devices also assisted Coldcard users, highlighting a community-driven "immune system" approach to crisis.
- David Bennett advises immediately migrating funds from any CoinKite product; he suggests using centralized exchanges like Coinbase or Kraken as a temporary measure if other self-custody options are untrustworthy or unavailable. He emphasizes avoiding panic and performing test transactions.
- David Bennett describes this incident as a "crossing the Rubicon" moment, where AI's ability to automate exploit discovery against vast code repositories means continuous, daily security audits are now essential. He suggests this creates a "security moat," raising costs for smaller projects.
- David Bennett proposes "swarm audits" where community members pool resources (AI tokens, compute, human review) to continuously vet open-source codebases. He successfully used Grok to audit Bitbox 02 Nova's code, underscoring the potential for collective vigilance.
- A "second layer" of sophisticated phishing attacks emerged, using truthful information about the Coldcard vulnerability, legitimate links, and urgent calls to action to trick users into revealing seed phrases or installing malicious software. David Bennett warns no legitimate manufacturer will ever ask for a seed phrase.
- David Bennett places sole blame on CoinKite founder Rulo Novak for the "shitty code" and systemic failure, rejecting attempts to extend liability to influencers like Matt Odell or Marty Bent, who are investors in CoinKite through their firm 1031.
RABBIT HOLE RECAP #421: CATASTROPHIC COLDCARD BUG • Aug 3
- A broken random number generator in Coldcard firmware leaves private keys vulnerable to immediate brute-force attacks.
- The era of trusting single-vendor hardware wallets is over, replaced by mandatory multisig and extreme paranoia.
- New AI models are identifying legacy code flaws in minutes, shortening the window for emergency migrations.
CATASTROPHIC COLDCARD BUG • Aug 3
- A critical vulnerability in Coldcard hardware wallets (versions 4.0.1 and later, or any model after 4.0.0) compromises private keys due to a faulty random number generator.
- The catastrophic Coldcard bug, introduced in March 2021, compromises seeds generated on any device after that date unless sufficient dice roll entropy (over 100 rolls) or a passphrase was used.
- Hosts advise all Coldcard users to immediately move their funds off the devices and to cease using the product entirely, regardless of previous protective measures like passphrases or multisig.
- The Coldcard vulnerability was publicly disclosed on August 3, 2023, at Bitcoin block height 960885, prompting hosts to release this podcast immediately to maximize user notification efforts.
- The hosts had previously conducted Coldcard workshops since December 2019 at Chaincode Labs with figures like Evan Kaludis and James O'Byrne, demonstrating features like dice rolls and passphrases.
- Hosts concede to complacency, having placed too much trust in CoinKite's NVK and Peter; they now believe the concept of a "magic bullet" beginner-friendly solution for high-value self-custody is dead.
- The Bitcoin community has rallied to assist affected users, with Rob Hamilton (@Roboneham on X) publishing an extensive guide detailing Coldcard vulnerabilities, migration options, and recovery steps.
- Attackers are actively brute-forcing compromised Coldcard seeds using GPUs, while authorities are investigating an attacker who reportedly pinged a centralized API provider to look up vulnerable addresses.
- The hosts clarify the vulnerability is entirely CoinKite's responsibility, stating their firm 1031 is a minority investor (under 10%) with NVK and Peter maintaining majority ownership and control.
- The hosts will now refrain from directly recommending specific custody solutions, instead laying out options and emphasizing multi-vendor multisig and robust passphrases as critical for long-term secure Bitcoin storage.
- Users are strongly advised not to update Coldcard firmware, as new releases may brick devices; instead, the immediate priority should be transferring all funds off the compromised hardware.
Also from this episode: (2)
Media (1)
- The hosts express deep regret and take accountability for recommending Coldcard for seven years, admitting their past confidence was misplaced despite consistently advocating "don't trust, verify."
AI & Tech (1)
- The bug, which existed for five years, appears to have been recently identified with assistance from AI, possibly through OpenAI's Cypher program utilized by Rob Hamilton's team for auditing Bitcoin projects.
Unpacking the Coldcard Exploit | FREEDOM TECH FRIDAY 50 • Aug 1
- A Coldcard hardware wallet exploit led to approximately 600 Bitcoin, valued at about $38 million, being emptied from around 500 single-signature wallets within 30 minutes.
- Q reports that updated estimates suggest over 1,000 Bitcoin have been stolen, emphasizing that the situation is still evolving and users who lost funds did nothing inherently wrong.
- The exploit affects Coldcard Mark 3 devices on firmware version 4.0.1 and later, Mark 4 and 5 devices before version 5.6, and Q devices on firmware 1.5 or earlier.
- The vulnerability stems from a core code rewrite in March 2021 that stopped using the device's hardware randomness for seed generation, instead relying on predictable software randomness.
- Q states that the crucial factor for determining risk is the firmware version on the Coldcard when the seed was *generated*, not the current firmware version.
- Seth advises all users to move funds from any seed generated on a Coldcard due to this issue, even if they used dice rolls or a passphrase, as the vulnerability window varies.
- Multi-vendor multisig users, such as a 2-of-3 setup, are safe from direct fund loss because one compromised Coldcard key is insufficient to move funds, but they should rotate the key.
- Zach explains that Foundation's Passport devices are not affected, as they combine multiple entropy sources including an open-source avalanche noise source, avoiding reliance on black-box silicon.
- Seth warns that privacy for non-Coldcard users could be damaged if they participated in coinjoins or payjoins with vulnerable Coldcard users, as transaction histories are now traceable.
- For migration, Seth advises moving individual UTXOs one at a time to unique addresses and randomizing timing to preserve privacy, though sweeping all funds is simpler for security-first users.
Also from this episode: (3)
Coding (1)
- If a user generated their seed with 50-98 independent dice rolls, they achieved 128 bits of entropy, bypassing the software bug. 99 or more rolls provided 256 bits of entropy.
Open Source (1)
- Zach attributes the bug to Coldcard's move away from free and open-source software (FOSS) in early 2021, replacing GPL code with a proprietary 'source available' library, LibNGU, which lacked community scrutiny.
Education (1)
- Q cautions against scammers and impersonators who will exploit the panic, reminding users to never give out seed words and to only use official channels for support.
What Bitcoin Did
Danny Knowles
EMERGENCY BITCOIN UPDATE: Coldcard Attack Explained | Rob Hamilton • Jul 31
- Rob Hamilton issued an urgent warning for Coldcard MK3, MK4, MK5, and Q users who generated wallets directly from the device without providing their own entropy or a strong passphrase, urging immediate fund recovery.
- The critical bug, introduced in early 2021 via a firmware change, compromised the entropy generation process, making seed words created by affected Coldcard devices insecure.
- Rob Hamilton clarifies that Coldcard MK1 and MK2 models are not impacted by this specific firmware bug, as they are older hardware and do not receive new firmware updates.
- For impacted Coldcard users, a sufficiently strong 25th-word passphrase or providing external entropy (e.g., dice rolling) is the only protection against attackers scanning all possible Coldcard seed phrases.
- Rob Hamilton explains that the MK3 has only 2^32 bits of entropy, which is easily brute-forced by consumer hardware, while MK4, MK5, and Q models have 45-50 bits, still vulnerable to GPU data farms.
- The vulnerability stems from a single line of code that incorrectly skipped secure entropy generation if a function merely existed, rather than evaluating if it was true, a 'nuclear event' for hardware wallet security.
- Danny Knowles confirms that Trezor and Foundation devices are safe because they do not use the same compromised library as Coldcard, indicating a specific, not widespread, self-custody vulnerability.
- Rob Hamilton recommends moving funds to trusted exchanges like River, citing its in-house custody and proof of reserves, or immediately acquiring other hardware wallets like Ledger or BitKey as emergency measures.
- Multi-signature wallets are at risk if a majority of their signers (e.g., two of three) are compromised Coldcard devices without strong passphrases or rolled dice; Unchained, Casa, and AnchorWatch state they are not affected.
- For at-risk multi-sig wallets with un-reused addresses, Rob Hamilton suggests using Mara Slipstream to broadcast transactions directly to a mining pool, which helps prevent replace-by-fee attacks by faster confirmation.
- Rob Hamilton estimates over 1100 BTC has been stolen already, with projections of thousands more, as well-capitalized attackers using GPU computing join the effort to exploit the vulnerability.
- The Coldcard incident is a 'nuclear event' for Bitcoin self-custody, fundamentally undermining the trust in hardware wallets to generate sufficiently random numbers, a core tenet of Bitcoin security.
- Future improvements for self-custody could include Bitcoin covenants and vault-like structures, enabling on-chain controls like address whitelisting or spending limits for enhanced security.
Also from this episode: (2)
BTC Markets (1)
- Initially, the attack was carried out by an amateur, evident from only targeting addresses with more than 0.15 BTC and failing to scan full addresses; now, multiple sophisticated attackers are involved.
Models (1)
- Rob Hamilton observed that bleeding-edge, open-source LLMs like Kimi K3, without safety guardrails, could instantly identify the Coldcard bug, signaling a new era where AI accelerates vulnerability discovery.
The COLDCARD Hack and Future of Self-Custody • Jul 31
- Steve estimates the Coldcard security incident has resulted in over 1,000 BTC stolen, valued between $65 million and potentially $100 million, describing it as the "worst day in Bitcoin's history" due to the impact on self-custody.
- The bug allows attackers to regenerate private keys from on-chain transactions due to weak entropy, without physical device access or seed phrases, by brute-forcing inputs like the CPU timer cycle and unique device ID.
- Steve advises Coldcard users in vulnerable situations to move funds immediately to temporary locations like trusted custodians or wiped, old devices; CoinKite has released new firmware for most products, but not MK3.
- Bitcoin itself is not compromised; this is a vendor-specific issue with CoinKite's Coldcard products, underscoring Max's argument that AI poses a more immediate and significant threat to security than quantum computing.
- Customers who properly used Coldcard's dice roll feature (e.g., 99-100 rolls) or a strong BIP39 passphrase (128-bit or more) should be safe, but Steve suggests moving funds for peace of mind.
- Steve emphasizes custody diversification as crucial, recommending users split funds between solutions with non-intersecting risks, such as a third-party custodian and a self-custody solution, rather than relying solely on one method.
- Steve suggests that recovering stolen Bitcoin would require proving original ownership through a combination of unique device IDs, DKIM-signed email receipts from CoinKite (verified for 2023), and KYC/on-chain analysis from exchanges.
- White hat hacking to sweep vulnerable funds to a secure system, to be returned to rightful owners, is proposed as a method to mitigate further theft, though the legality and feasibility remain uncertain.
- Multi-signature setups remain a strong self-custody option, but require diversity across keys from different hardware/software vendors to avoid single points of failure, unlike using multiple devices from the same vendor.
- BitKey is a multi-signature product by default, using three keys generated across different hardware and software stacks (Block server, phone, hardware device) to provide diversity, but it lacks independent verifiability for some key generation processes.
Also from this episode: (5)
Chips (2)
- The Coldcard vulnerability affects MK2 and MK3 hardware with firmware from 2021 to the present, stemming from a compile-time bug that caused the hardware random number generator to fall back to a weak software pseudo-random generator.
- Newer Coldcard models (MK4, MK5, Q) have 32 to 72 bits of cryptographic entropy, which is stronger but still potentially vulnerable to a financially substantial brute-force attack; reports indicate these models have also been exploited.
Models (1)
- Max proposes that for critical software, users need transparency on which top-tier AI models are conducting 24/7 security audits, stating that "all bugs are shallow with enough tokens."
Open Source (1)
- Project Loupe, launched by Spiral, performs AI security scans on open-source Bitcoin repositories, but models produce noise and misclassify severity, necessitating human review and active remediation by project maintainers.
ETFs (1)
- Max questions if retail users can perform in-kind BTC transfers to IBIT (BlackRock's ETF) without a taxable event, noting it's currently restricted to authorized participants with tens of millions of dollars.
TFTC: A Bitcoin Podcast
Marty Bent
777: Coldcard Is Compromised with James O'Beirne • Jul 31
- Marty Bent argues Bitcoin will emerge as the victor over fiat currencies in a world where central banks actively devalue their money.
- A critical vulnerability affects Coldcard hardware wallets, manufactured by CoinKite, produced after 2021, specifically MK2 and MK3 models with firmware between 2021 and 2023.
- The vulnerability stems from an insufficient random number generator (RNG) used for private keys, making them deterministic and severely limiting the search space for recovery.
- Users are secure if they initiated their Coldcard key with over 99 dice rolls or used a sufficiently complex passphrase, which is often longer than users anticipate.
- Current Coldcard devices, including the Q model, are estimated to provide only 70 bits of security during key generation, far below the intended 256 bits.
- Guest highlights that updating firmware alone does not fix the vulnerability; users must generate a new private key pair and migrate funds to the new address.
- Marty Bent clarifies that MK2 and MK3 models generated after 2021 with default settings might offer as little as 30 bits of entropy, requiring urgent fund migration.
- Marty Bent notes that AI models are becoming sophisticated enough to uncover such security vulnerabilities, with Kimmy K3 reportedly used to discover this Coldcard flaw.
- Guest expresses concern that the Coldcard incident could damage trust in self-custody among Bitcoiners and the broader public, despite best practices like multi-vendor setups.
- Past incidents include Ledger spilling client data multiple times and BitBox having physical defects allowing key exfiltration, underscoring the inherent difficulty of hardware wallet security.
- Guest suggests that while auditing RNGs is crucial, the ultimate fix for improved user experience and multisig-level security lies in on-chain covenant technology.
- Multi-signature setups are safe from the Coldcard vulnerability if at least one critical signing key is generated by a non-CoinKite device unaffected by the bug.
- Guest quotes Nick Szabo's principle that 'trusted third parties are security holes,' reinforcing the lesson that delegating security fully to a packaged product is risky.
- Marty Bent asserts that US government intervention in 'model wars' by 'cucking' frontier AI models like Fable 5 and ChatGPT 5.6 hinders crucial security auditing for Bitcoin systems.
- Guest observed that US-based AI models censored or blocked inquiries related to the Coldcard vulnerability, making security investigations more difficult compared to less restricted models.
- The hosts debated the ethical implications of 'white hats' using computing resources to sweep vulnerable funds from exposed Coldcards, citing challenges in attributing and returning funds.
- As a temporary measure, individuals with affected Coldcards are advised to move their funds to a trusted exchange, performing small test transactions first to avoid errors.
- A passphrase composed of six BIP39 words is generally not considered strong enough, as the search space for 2048 words multiplied by six is still too small for robust security.
Also from this episode: (1)
Models (1)
- The hosts caution that the rise of AI is accelerating the erosion of 'security by obscurity,' making all open-source code and historical versions vulnerable to automated analysis.
Square Engineering
Square Engineering
Predictable RNG Fallback and 32-Bit Reseed in COLDCARD Firmware • Jul 30
- Block's security research identified vulnerabilities in COLDCARD firmware that could enable Bitcoin theft, stemming from an RNG integration error causing `ngu.random` to default to MicroPython's deterministic Yasmarang fallback.
- COLDCARD Mk2/Mk3 v4.0.0-v4.1.9 firmware versions have no cryptographic entropy added to `ngu.random`, making wallet generation deterministic if the device UID, timer state, and RNG-call history are known.
- An attacker with knowledge or sufficient constraints on device UID, timer state, and RNG-call history can reproduce the fallback stream offline, potentially recovering wallet seeds and private keys.
- For Mk2/Mk3 v4, the maximum enumeration count under normal cold-boot with known UID but unknown SysTick is approximately 2^16.29, making the seed highly vulnerable.
- Current devices like Mk4/Q/Mk5, even with a successful reseed, have a secure-element-derived search space limited to at most 2^32 possibilities when the fallback state and call history are known.
- The vulnerability affects other functionalities relying on `ngu.random`, including paper-wallet private keys, seed XOR masks, cloning/USB encryption keys, Key Teleport, Web2FA, and Secure Notes passwords.
- The regression originated from a firmware change on March 1, 2021, which migrated wallet generation to `libngu`, and appeared in released firmware v4.0.0 on March 17, 2021.
Also from this episode: (4)
Coding (1)
- The vulnerability arises because the production board configuration defines `MICROPY_HW_ENABLE_RNG` as zero, and `libngu` incorrectly checks if the macro is defined rather than enabled, binding to a deterministic software generator.
Chips (2)
- COLDCARD Mk4/Q/Mk5 devices, using production firmware v5.0.0 onward, incorporate a limited secure-element reseed that hashes 32 bytes to retain only four, replacing just one 32-bit Yasmarang state word.
- The Yasmarang software fallback initializes using the MCU's low 32-bit UID, SysTick counter, and RTC registers, none of which are cryptographic entropy sources, allowing for state reproduction.
Safety (1)
- Block and security researchers identified the root cause on July 30, 2026, after user reports of lost funds, leading to the early publication of this advisory due to ongoing active exploitation.