Cryptographic Vulnerabilities Discovered by Claude Mythos Preview

Occurred 21 April 2026Date inferred from coverage

Anthropic's Claude Mythos Preview model has identified mathematical flaws in cryptographic algorithms, specifically impacting a post-quantum digital signature candidate (HAWK) and a variant of the Advanced Encryption Standard (AES). While these findings demonstrate advanced autonomous research capabilities, Anthropic reports they do not currently affect production systems.

Aggregated from 6 sources · Updated 26 Aug 2026, 03:04 UTC (UTC)

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Facts (11)

Established
Claude Mythos Preview identified a mathematical vulnerability in HAWK, a digital signature scheme designed for post-quantum security.
Established
The HAWK attack reduced the expected cost of full key recovery for the HAWK-256 parameter set from 2^64 to 2^38 operations.
Established
Claude Mythos effectively halved HAWK's security margin, potentially requiring a doubling of key sizes to maintain original security levels.
Established
Mythos discovered a way to improve the speed of existing attacks on a reduced-round version of the Advanced Encryption Standard (AES) by 200-800x.
Established
The HAWK vulnerability involved identifying a previously unexploited symmetry, or non-trivial automorphism, in the lattice structure of the algorithm.
Established
Claude Mythos Preview is not available for public release due to concerns regarding its potential use in developing automated cyberattacks.
Established
Project Glasswing was launched to provide restricted access to the model for critical infrastructure organizations and cybersecurity defenders.
Established
Anthropic states that the cryptographic findings currently have no practical impact on production systems or deployed software.
EmergingNiche Signal
The model identified an attack on 13 rounds of the Korean LEA block cipher standard that can recover a key in under an hour on a desktop computer.
EmergingNiche Signal
Anthropic researchers spent approximately $100,000 in API credits for each of the two cryptographic studies.
EmergingNiche Signal
The UK AI Security Institute found that Mythos Preview could solve a 32-step simulated corporate network attack in 3 out of 10 attempts.