Anthropic's Frontier Red Team said on Tuesday that Claude flagged 493 attack-surface issues across 25 open-source projects totaling more than five million lines of code. Rather than hunting individual bugs, Claude mapped which code an attacker can actually reach, then helped gate whatever a deployment does not need to expose.

Claude inventoried more than 17,000 configuration options, 3,842 of them security-relevant, and found 162 risky combinations — in 94 cases, combining options silently turned off a security control. All 11 login-gated projects had code reachable before authentication that did not need to be there, and one conflicting pair of options that let a certificate-only server accept anyone had survived for 21 years.

The sharpest case is OpenSSH: Claude traced about 4,500 lines of experimental ML-DSA-44 signature code reachable before login, about 16% of the default pre-authentication surface. Fixes in OpenSSH 10.6 removed roughly a fifth of the code an unauthenticated client could previously reach. Anthropic is explicit that the method does not remove unknown vulnerabilities — it makes them harder to reach.