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Fiber Admin 3.1.0 — 4.0.0 - Unauthenticated Remote Code Execution

CVE-2026-121491Published · Updated

Action summary

Affected: 3.1.0 – 4.0.0Update to 4.0.1 or newer

All remediation steps
Watch plugin
Severity
Critical9.8
CVSS
9.8
CVSS 3.1 · CNA (Wordfence)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
What does this vector mean?
AV:N Attack vector
Network
AC:L Attack complexity
Low
PR:N Privileges required
None
UI:N User interaction
None
S:U Scope
Unchanged
C:H Confidentiality
High
I:H Integrity
High
A:H Availability
High
Weakness
CWE-94 Improper Control of Generation of Code
Required access
No account needed
Exploit prediction (EPSS)
0.4% chance in 30 days34th percentile
CISA KEV
Not listed
On this page8

Am I affected?

Fiber Admin fiber-admin

  1. Affected3.1.0 – 4.0.0
  2. Patched in4.0.1

Update to 4.0.1 or newer.

You are affected if you run 3.1.0 – 4.0.0. Version 4.0.1 and later are not affected by this issue.

  • Check your version: in wp-admin go to Plugins → Installed Plugins and read the version under Fiber Admin.
  • No admin access? Run a passive check of your site. It reads public files only.
  • No account is needed to exploit this. Treat any exposed site on an affected version as at risk.

What to do

  1. Update to version 4.0.1, or a newer patched version
  2. Rotate administrator passwords and application secrets if the site ran a vulnerable version while publicly reachable.
  3. Watch Fiber Admin to get an email when the next vulnerability is published.

Advisory

Source description from Wordfence Intelligence, credited to Naoki Kawahigashi.

The Fiber Admin plugin for WordPress is vulnerable to Remote Code Execution in versions 3.1.0 through 4.0.0. This is due to insufficient validation of user supplied input before it is executed. This makes it possible for unauthenticated attackers to execute arbitrary code on the server.

Exploits & references

Proof-of-concept & detection

No public proof-of-concept or detection template is known for this vulnerability.

Advisories & patches

More in Fiber Admin

All 2
More vulnerabilities in Fiber Admin
SeverityVulnerabilityCVEPublished
Medium5.3Missing Authorization
≤4.0.0Update to 4.0.1
CVE-2026-121492

Timeline

  1. CVE published

    Severity critical, CVSS 9.8

  2. Record last updated

Sources & licenses

Wordfence record
Vulnerability data
Wordfence Intelligence. Copyright 2012-2026 Defiant Inc. Licensed under the CC BY-SA 4.0.
CVE® identifiers
Copyright 1999-2026 The MITRE Corporation. Used under the CVE Program. CVE® is a registered trademark of The MITRE Corporation.
CVSS / CWE
National Vulnerability Database (NVD), shown unmodified. This product uses the NVD API but is not endorsed or certified by the NVD.
EPSS
Exploit Prediction Scoring System by FIRST.org.
VulnCrest content
Summary, remediation guidance and page layout © VulnCrest. Not sourced from NVD.

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