Authentication Bypass by Capture-replay in mod_auth_openidc - #VU142426
Published: August 13, 2026
Vulnerability identifier: #VU142426
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-294
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to replay back-channel logout tokens.
The vulnerability exists due to improper authentication in back-channel logout token validation when accepting logout tokens without required iat or jti claims. A remote attacker can resend a previously accepted logout token to replay back-channel logout tokens.
The affected behavior removes the freshness and replay protections provided by those claims.
Affected software
mod_auth_openidc
Remediation
Install security update from vendor's website.
mod_auth_openidc - update to 2.4.20.1