mod_auth_openidc vs Expo

This is the Apache module implementing OpenID Connect relying-party support, and its 2.4.20.x line has been an almost unbroken security programme. An internal audit turned up eight issues including an identity-header bypass; PBKDF2 key stretching changed the session encryption key and invalidated every session created by 2.4.19.x and earlier; out-of-bounds reads and writes were fixed in the state-cookie parser. The latest release continues in the same register, hardening file-backed metadata and cache I/O and the shared-memory cache itself.

The project is working outward from the code paths an attacker actually reaches: cookie parsing, then session key derivation, then cache storage and the files the module reads at runtime. Keyed hashing of cache keys to stop bucket-chain flooding, refusing non-regular files, capping allocations and writing metadata atomically all address resource-exhaustion and file-substitution classes rather than single bugs. Packaging and commercial distribution notes take up an increasing share of each release body, with Redis and Valkey over TLS behind a commercial agreement.

With the cache and file layers now hardened, the remaining large surface is the HTTP client and provider metadata handling, so that is the likeliest next area — and the 2.4.20.x line should settle into ordinary maintenance once the audit backlog is worked through.