COLDCARD Security News August 1, 2026: Fixing Firmware Is Not Enough
Coinkite released fixed firmware for affected COLDCARD models, but existing weak seeds remain exposed. Here is how to identify the risk and migrate without rushing.
COLDCARD security news on August 1, 2026: fixed firmware cannot repair an old seed
Coinkite confirmed on July 31 that fixed firmware is available for every affected COLDCARD model and release track after an entropy bug put some Bitcoin wallet seeds at risk. The update prevents the affected seed-generation path from being used again. It does not make an existing weak seed safe.
That distinction is the urgent part. A user whose seed was generated on affected firmware generally needs to install the correct fixed release, create a completely new seed, verify the new wallet, and move funds to it. Simply updating the device while continuing to use the old seed leaves the original exposure in place.
Coinkite's advisory covers Mk3 seeds generated on firmware 4.0.1 through 4.1.9, as well as seeds generated on Mk4, Mk5, and Q devices before their fixed releases. The company said an exception may apply when at least 50 fair, independent, private dice rolls were added during the original seed creation, but users who cannot verify that condition should follow the migration guidance.
1. The bug sent seed generation to a predictable software path
Coinkite traced the problem to a 2021 integration change made while moving elliptic-curve operations to Bitcoin Core's widely used `libsecp256k1` library.
The cryptographic library was not the problem. The integration changed wallet seed generation from a path that reached the device's hardware random-number generator to one that resolved to MicroPython's deterministic software fallback.
Two functions had compatible interfaces, so the firmware built successfully. Existing review confirmed that the intended hardware-randomness implementation was present in the binary, but it did not verify which implementation the wallet seed-generation path actually reached across the submodules.
Coinkite's current estimate is that affected Mk3 seeds had about 40 bits of effective entropy rather than the intended 128 bits. Later Mk4, Mk5, and Q devices mixed in additional secure-element data, but Coinkite still estimates only about 72 bits under its current assumptions.
Block's Bitcoin Engineering and Security team published a coordinated analysis that is more conservative about the later devices. It found that only four bytes of secure-element-derived data reached the software generator's reseed operation, limiting the number of securely distinguished output streams under the analyzed conditions.
Both reports reach the same practical conclusion: affected seeds should not be treated as having the security level users expected.
2. Which fixed firmware version applies to each device
Coinkite updated its advisory on July 31 at 12:39 p.m. EDT to list emergency fixes for every affected model and both release tracks.
| Device and track | Fixed version |
|---|---|
| Mk3 | 4.2.0 or later |
| Mk4 or Mk5 standard | 5.6.0 or later |
| Q standard | 1.5.0Q or later |
| Mk4 or Mk5 Edge | 6.6.0X or later |
| Q Edge | 6.6.0QX or later |
Standard and Edge are separate tracks. An Edge user needs the fixed Edge release for the device; an older Edge 6.x version is not safe merely because its number is higher than a standard 5.x release.
The fixed firmware corrects new seed generation. It does not rewrite, strengthen, or otherwise repair seed words created before the fix.
Coinkite said TAPSIGNER, OPENDIME, and SATSCARD are not affected because they use different codebases.
3. Updating and migrating are two separate jobs
The safe sequence matters because a hurried migration can create its own loss risk.
Coinkite's guidance is to:
- confirm the correct fixed firmware is installed for the model and release track
- generate a completely new seed on the updated device
- record and verify the new backup before sending funds
- verify the new wallet fingerprint and a receive address on the device screen
- send a small test transaction and confirm it arrived
- move the remaining funds only after the test succeeds
- keep the old backup until the entire migration is confirmed
Users should obtain firmware only from the official COLDCARD download pages and verify the version on the device. A replacement wallet should use a newly generated seed; importing the same affected words into another hardware or software wallet does not remove the weakness.
A BIP-39 passphrase creates a separate wallet and may add an independent barrier when it is strong and unique. It is not the device PIN, and it is not a reason to postpone migration. Losing or mistyping the passphrase can also make funds inaccessible, so the wallet fingerprint and receive address must be checked before deposits.
4. The dice-roll exception is narrow
Affected firmware hashed user-supplied dice input together with the device-generated seed. Coinkite said 50 to 98 fair, independent, private rolls contributed at least 128 bits of entropy, while 99 or more contributed approximately 256 bits.
That exception applies only when the user knows the rolls were:
- added during creation of the final seed now securing the wallet
- produced independently with a fair six-sided die
- kept private and never recorded or exposed
- at least 50 in number
If fewer than 50 rolls were used, the count is uncertain, or the user cannot confirm which final seed included them, Coinkite says to migrate.
The dice sequence itself is secret key material. It should never be photographed, stored digitally, or entered into a website or networked computer.
5. Active exploitation changes the response threshold
Block said its report was published early because active exploitation was under way. Bitcoin Optech's July 31 action notice also told users with potentially affected COLDCARD-generated keys to move funds carefully to an unaffected wallet.
This is not a routine update where users can assume the vulnerable behavior matters only the next time they create a wallet. The weak output was used to create the key material protecting existing funds.
The public reports do not establish that every affected seed can be recovered immediately by any remote attacker. Practical attack cost depends on device details, timing state, prior random-generator calls, and the work needed to test candidate seeds. That uncertainty should not be treated as protection when the manufacturer and independent researchers both recommend replacement.
Users should also expect impersonation and phishing around a high-profile wallet incident. Coinkite's migration steps do not require entering seed words on a support site, sharing them with staff, or installing firmware from an email link.
What happened on the key dates
| Event | Exact date | What was confirmed |
|---|---|---|
| The faulty seed-generation path entered released Mk3 firmware | March 2021 | Coinkite traced the regression to the 4.0.1-era integration change |
| Users reported unexpected wallet transactions | July 29-30, 2026 | Researchers began tracing the thefts to insufficient seed entropy |
| Coinkite and Block published their initial reports | July 30, 2026 | The manufacturer and independent researchers documented the RNG integration failure and affected generations |
| Coinkite updated the advisory with all fixed releases | July 31, 2026 | Fixed standard and Edge firmware was available for Mk3, Mk4, Mk5, and Q devices |
Why this matters for KrptoPay users
- offline signing cannot protect a wallet whose seed was predictable when created
- firmware updates can prevent future exposure without repairing existing keys
- moving the same seed to a different device preserves the original weakness
- a migration should start with version and address verification, then a small test transfer
- urgent security news is also a phishing opportunity, so seed words must remain offline and private
Frequently asked questions
Q: Is every COLDCARD wallet affected?
A: No. Exposure depends on the device model, release track, and firmware used when the seed or other secret was generated. Coinkite's advisory lists the affected ranges and fixed versions.
Q: Does installing the latest firmware secure my existing seed?
A: No. The update fixes new seed generation. An existing seed created by affected firmware remains the same and generally needs to be replaced through a careful wallet migration.
Q: Can I import the old seed into another hardware wallet?
A: Importing the same words into another device does not add entropy to them. Funds must be moved to addresses controlled by a newly generated, verified seed.
Q: Are seeds made with dice safe?
A: Coinkite says the RNG issue alone does not put a seed at risk when at least 50 fair, independent, private dice rolls were added during its creation. Users who are unsure about the count, privacy, or final seed should migrate.
Q: Should I move all funds in one transaction?
A: Coinkite recommends verifying the new backup, fingerprint, and receive address, then sending a small test transaction first. The remaining balance should move only after the test is confirmed.
Q: What should I never share during this process?
A: Never share seed words, a BIP-39 passphrase, dice-roll sequences, or private keys. The official migration does not require entering them into a website or giving them to support staff.
Sources
- Coinkite COLDCARD security advisory, published July 30 and updated July 31, 2026
- Coinkite technical backgrounder on the entropy issue, updated July 31, 2026
- Block Engineering analysis of the predictable RNG fallback, published July 30, 2026
- Bitcoin Optech Newsletter #416 action notice, published July 31, 2026
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