Anthropic Frontier Red Team: using Claude to perform attack surface reduction on 25 open-source projects, finding 493 issues; 94 configuration combinations silently disable security controls, and under OpenSSH's default configuration unauthenticated clients can reach about 4500 lines of experimental ML-DSA code

Anthropic's Frontier Red Team used Claude to perform automated attack surface analysis on 25 open-source projects (over 5 million lines of code), finding 493 issues in total. The method falls into three categories: code reachable under default configuration but not intended for use, configurations that are reasonable individually but silently disable security controls when combined, and early reachable code executed before security controls such as authentication. Of these, 162 security-related configuration combinations were accepted without warnings, and 94 silently disable security controls. In the OpenSSH case, under the default configuration unauthenticated clients can reach about 4500 lines of experimental ML-DSA-44 code, about 16% of the default sshd pre-authentication code, which was fixed in versions 10.5 and 10.6 after being reported. The team integrated the method into a reusable Claude skill and is integrating it into OSS-Scanner.