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Yoast SEO Premium - Remote Code Execution (CVE-2026-10821)

CVE-2026-10821

Vulnerability CVE-2026-10821 PLUGIN yoast-seo-premium MEDIUM

The Yoast SEO Premium WordPress plugin before 27.6.1 does not sanitize control characters from redirect origins before writing them to the site's Apache configuration file when the file-based redirect mode is enabled, and the redirect-creation endpoint is reachable by users with only Author-level access. This allows such users to inject arbitrary newline-delimited Apache directives into the root .htaccess file. On Apache servers that honour PHP directives, the injection can be chained with the user's own media upload (a polyglot image carrying a PHP payload) and an auto_prepend_file directive to achieve Remote Code Execution.

CVE-2026-10821

MEDIUM CVSS 6.6 Published 2026-09-02 Updated 2026-09-03
AI Risk Elevated (65/100) Active Exploit: No strong signal Published Exploit: No public exploit references Priority: P3 Priority
Severity Band MEDIUM
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
Affected Components 1
Reference Links 2
AI Risk Engine Elevated (65/100)
Exploitability High
Active Exploitation No strong signal
Published Exploit Status No public exploit references

Threat Timeline

  1. 2026-09-02 CVE published and first recorded in the threat feed.
  2. 2026-09-03 Record updated with latest vulnerability metadata.
  3. 2026-09-03 AI technical context refreshed for mitigation and impact guidance.
  4. Now Monitoring for follow-up changes, linked references, and new related CVEs.

AI Context

Machine-generated threat intelligence

AI Updated 32 days ago

AI enriched 32 days ago (2026-09-03 10:17 UTC)

Technical Summary

The Yoast SEO Premium WordPress plugin before 27.6.1 does not sanitize control characters from redirect origins before writing them to the site's Apache configuration file when the file-based redirect mode is enabled, and the redirect-creation endpoint is reachable by users with only Author-level access. This allows such users to inject arbitrary newline-delimited Apache directives into the root .htaccess file. On Apache servers that honour PHP directives, the injection can be chained with the user's own media upload (a polyglot image…

Potential Impact

Severity is MEDIUM (CVSS 6.6). Depending on deployment context, affected components may be exposed to unauthorized actions or data integrity risk.

Exploitability Assessment

Exploitability is assessed as High based on remote code execution potential.

Primary risk drivers: remote code execution potential

Mitigation Recommendations

Validate affected product versions, prioritize patching, and monitor references for vendor remediation guidance. If immediate patching is not possible, apply compensating controls and limit exposure of vulnerable surfaces.

Detection & Monitoring

Track authentication anomalies, unexpected file writes, and suspicious plugin API activity around affected components.

Business Impact Lens

AI risk score 65/100 (Elevated, High) with priority P3 Priority. Prioritize remediation where affected components process customer data, admin sessions, or Internet-exposed workflows.

Affected Products

Yoast SEO Premium PLUGIN · yoast-seo-premium Affected: < 27.6.1 Fixed in: 27.6.1

References

What to do about this

Patch promptly The consequence is significant even where an attacker needs a foothold first.

Fix it

Update Yoast SEO Premium to 27.6.1 or later.

That is the complete fix. Everything below is what protects you in the meantime.

Cannot update today? Request / payload inspection (WAF) in Hack Halt ProSecure blocks this class of attack before WordPress processes the request.

Inspect request parameters and bodies for injection, traversal and file-inclusion payloads, and refuse the request rather than logging it.

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Not sure if you are affected?

Scan your site to see whether it runs Yoast SEO Premium, and at which version.

Free, no installation, no account. It reads what your site already publishes, then tells you which plugins carry known vulnerabilities and what to do about each one.

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Am I affected by this vulnerability?

You are affected if your site runs Yoast SEO Premium. Versions below 27.6.1 are vulnerable; that release and later are not.

How do I fix it?

Update Yoast SEO Premium to version 27.6.1 or later. That is the complete fix. Until you can update, Request / payload inspection (WAF) in Hack Halt ProSecure contains this class of attack at the request layer.

What can an attacker actually do?

This is a Remote Code Execution flaw. An attacker who exploits it can run their own code on the server, which is total control of the site.

WordPress security that blocks attacks before they land.

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