Yoast SEO Premium < 27.6.1 - Author+ Arbitrary .htaccess Directive Injection to RCE

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-10821
StatePUBLISHED
AssignerWPScan
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-02 15:17:37 UTC
Updated2026-09-03 17:50:37 UTC
DescriptionThe 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.

Risk And Classification

Primary CVSS: v3.1 6.6 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.005120000 probability, percentile 0.418010000 (date 2026-09-07)

Problem Types: CWE-74 | CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection') | CWE-74 CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.6MEDIUMCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED6.6MEDIUMCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
High
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Unknown Yoast SEO Premium affected 27.6.1 semver Not specified

References

ReferenceSourceLinkTags
yoast.com/yoast-seo-premium-may-26-2026 [email protected] yoast.com
wpscan.com/vulnerability/2ddd8362-7248-48de-aab9-74c70e7d5dd6 [email protected] wpscan.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Tin Pham (TF1T) (en)

CNA: Trong Pham (dtro) (en)

CNA: Hao Ngo (en)

CNA: WPScan (en)

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