Vulnerability in Yoast Seo Premium
CVE-2026-10821
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.6 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.005 (42.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 42nd percentile — 42.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000
Affected products
- Yoast Seo Premium
Weakness classification (CWE)
References
- wpscan.com/vulnerability/2ddd8362-7248-48de-aab9-74c70e7d5dd6/ (technical-description, exploit, vdb-entry)
- yoast.com/yoast-seo-premium-may-26-2026/ (vendor-advisory)
Frequently asked questions
- What is CVE-2026-10821?
- CVE-2026-10821 is a medium-severity vulnerability in Yoast Seo Premium, classified under Improper Neutralization of Special Elements in Output Used by a Downstream Component (Injection). CVSS score: 6.6/10. Published 2026-09-02.
- How severe is CVE-2026-10821?
- Medium severity. CVSS v3 base score is 6.6 out of 10.