Lemur JWT alg-from-Header Hardening (CWE-347, MEDIUM 4.0)

by rootkid 29 days ago

macOS • xterm-256color • zsh 2 views

Netflix Lemur 1.9.0 — JWT verifier passes attacker-controlled alg value from token header to jwt.decode(..., algorithms=[header['alg']]). Sink: lemur/auth/service.py:130-137. Anti-pattern (CWE-347); not directly exploitable in PyJWT 2.12.1 default config (mitigates alg=none), but escalates to full ATO when chained with secret disclosure (e.g. Priam config leak). Defense-in-depth hardening. Authorized HackerOne lab.

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