CriticalCritical vulnerability

CVE-2026-121491 (CVSS 9.0)

NVD · officialPublished Nov 7, 2026Risk 50/100EPSS 0.4%

The Fiber Admin WordPress plugin before 4.0.1 does not validate or escape a request header before writing it into a PHP file it regenerates on an unprotected admin hook, allowing unauthenticated attackers to execute arbitrary code when its custom database error page is enabled and they win a race against an administrator saving its settings.

Technical details

CVSS

9.0

AV:NetworkAC:HighPR:NoneUI:NoneC:HighI:HighA:High

Evidence and sources

This record is attributed to NVD. Exploitation status and remediation guidance are kept separate from the vulnerability's technical severity.

Open primary source