CVE-2026-121491
Fiber Admin 3.1.0 - 4.0.0 - Unauthenticated RCE via Host Header
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Fiber Admin 3.1.0 - 4.0.0 - Unauthenticated RCE via Host Header
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.
- Record
CVE-2026-121491- CVSS 3.1
- 9.0 Critical
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H - Weakness
- CWE-94
- Updated
- 2026-11-07
EUVDEUVD-2026-118943
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.
- Record
EUVD-2026-118943- CVSS 3.1
- 9.0 Critical
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H - Updated
- 2026-11-07
GitHub AdvisoriesGHSA-qr57-vj96-mp6j
The Fiber Admin WordPress plugin before 4.0.1 does not validate or escape a request header before...
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.
- Record
GHSA-qr57-vj96-mp6j- CVSS 3.1
- 9.0 Critical
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H - Weakness
- CWE-94
- Updated
- 2026-11-07
NVD
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.
- Record
CVE-2026-121491- CVSS 3.1
- 9.0 Critical
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H - Weakness
- CWE-94
- Updated
- 2026-11-07
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| cwes, severity | CVE List | |
| severity | EUVD, NVD | |
| published | EUVD | |
| published | EUVD | |
| aliases, published | EUVD | |
| aliases, references | GitHub Advisories | |
| first indexed | CVE List |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-121491 is a critical vulnerability (CVSS 9.0) in Unknown Fiber Admin, published November 7, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.22%, the 13th percentile. No source names a fixed version.