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Coldcard Firmware Update After $114M Theft Due to Seed-Generation Flaw

Coldcard Firmware Update After $114M Theft Due to Seed-Generation Flaw

First seen 21 Aug 2026, 19:18 UTC • •

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ThreatCluster AI
ThreatCluster •August 22, 2026 at 18:51 UTC
  • •Coldcard firmware 5.6.1 released to mitigate a seed-generation vulnerability exploited in an attack.
  • •The exploit resulted in a loss of $114 million (1,816 BTC) from affected hardware wallets.
  • •Users must upgrade firmware to secure new seed generation; existing vulnerable seeds remain unsafe.

Coldcard has released firmware 5.6.1 to address a seed-generation vulnerability exploited in an attack that drained $114 million (1,816 BTC) from users' hardware wallets. The vulnerability affected customers using Mk4, Mk5, and Q devices, allowing hackers to exploit weak seed generation methods. The update introduces mandatory user-provided randomness for seed generation and strengthens transaction integrity checks. Users are advised to upgrade immediately, as existing vulnerable seeds remain unsafe. Coldcard is assisting law enforcement in investigating the thefts and continues to support affected customers in migrating their funds. The update also includes enhancements unrelated to the seed issue, such as improved USB data handling and multisig protections.

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Timeline

2026-07-31
Hotfix released for seed-generation vulnerability
Coldcard issued a hotfix addressing the seed-generation flaw, but the vulnerability was still exploitable for existing seeds.
blog.coinkite.com
2026-08-01
Seed-generation vulnerability disclosed
Coldcard revealed a critical vulnerability in seed generation that was actively exploited, leading to significant financial losses.
Cryptobriefing
2026-08-21
Firmware 5.6.1 released
Coldcard released firmware 5.6.1, enhancing security measures and urging users to upgrade to protect against the exploit.
blog.coinkite.com
2026-08-21
Ongoing investigation by law enforcement
Authorities are investigating the thefts linked to the seed-generation vulnerability and are working to identify the perpetrators.
blog.coinkite.com

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