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

Description

ApostropheCMS 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.

Scores

EPSS (exploitation in 30 days)

0.25% · top 84% of all CVEs (6 Nov 2026)

CISA SSVC

Exploitation: poc · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.1.

Weakness

• CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (opens in a new tab)All about CWE-79 and its CVEs

Affected products

• apostrophecms · apostrophe

  • affected >= 4.28.0, < 4.29.0

• apostrophecms · sanitize-html

  • affected >= 2.17.1, < 2.17.2

Affected packages

From reviewed advisories of the GitHub Advisory Database.

• npmsanitize-htmlGHSA-9mrh-v2v3-xpfm (opens in a new tab)

References (2)

• https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-9mrh-v2v3-xpfm (opens in a new tab)x_refsource_CONFIRM
• https://github.com/apostrophecms/apostrophe/commit/7ca2d16237c72718ef7e5c7ae0458e6027ac4f64 (opens in a new tab)x_refsource_MISC

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisory GHSA-9mrh-v2v3-xpfm (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-40186](https://trackcve.app/badge/CVE-2026-40186.svg)](https://trackcve.app/cve/CVE-2026-40186)

Record last updated 16 Apr 2026, 14:15 UTC.