ApostropheCMS: sanitize-html allowedTags Bypass via Entity-Decoded Text in nonTextTags Elements

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Summary

CVECVE-2026-40186
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-15 21:17:27 UTC
Updated2026-04-15 21:17:27 UTC
DescriptionApostropheCMS is an open-source Node.js content management system. A regression introduced in commit 49d0bb7, included in versions 2.17.1 of the ApostropheCMS-maintained sanitize-html package bypasses allowedTags enforcement for text inside nonTextTagsArray elements (textarea and option). ApostropheCMS version 4.28.0 is affected through its dependency on the vulnerable sanitize-html version. The code at packages/sanitize-html/index.js:569-573 incorrectly assumes that htmlparser2 does not decode entities inside these elements and skips escaping, but htmlparser2 10.x does decode entities before passing text to the ontext callback. As a result, entity-encoded HTML is decoded by the parser and then written directly to the output as literal HTML characters, completely bypassing the allowedTags filter. An attacker can inject arbitrary tags including XSS payloads through any allowed option or textarea element using entity encoding. This affects non-default configurations where option or textarea are included in allowedTags, which is common in form builders and CMS platforms. This issue has been fixed in version 2.17.2 of sanitize-html and 4.29.0 of ApostropheCMS.

Risk And Classification

Primary CVSS: v3.1 6.1 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Problem Types: CWE-79 | CWE-79 CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.1MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
3.1CNADECLARED6.1MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Apostrophecms Apostrophe affected >= 4.28.0, < 4.29.0 Not specified
CNA Apostrophecms Sanitize-html affected >= 2.17.1, < 2.17.2 Not specified

References

ReferenceSourceLinkTags
github.com/apostrophecms/apostrophe/commit/7ca2d16237c72718ef7e5c7ae0458... [email protected] github.com
github.com/apostrophecms/apostrophe/security/advisories/GHSA-9mrh-v2v3-xpfm [email protected] github.com
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NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
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