CVE-2026-54789: Openidc Mod Auth Openidc

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

mod_auth_openidc is an OpenID Certified authentication and authorization module for the Apache 2.x HTTP server that implements the OpenID Connect Relying Party functionality. Prior to 2.4.19.4, an out-of-bounds read and a one-byte out-of-bounds write exist in the state-cookie parser of `mod_auth_openidc`. The issue is fixed in version 2.4.19.4 by stopping the scan at the string terminator so a value-less token is rejected. No in-product workarounds are available. As a stop-gap, an upstream reverse proxy or WAF that rejects or normalizes malformed `Cookie` headers (tokens lacking `=`) can reduce exposure, but upgrading is the recommended remediation.

Affected products

• Openidc Mod Auth Openidc: before 2.4.19.4 (fixed in 2.4.19.4)

Published 2026-08-21. Last modified 2026-09-18.