Vulnerability 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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Apostrophecms | Apostrophecms | 4.29.0 |
| Apostrophecms | Sanitize-Html | <= 2.17.1 |
Related Weaknesses (CWE)
References
- https://github.com/apostrophecms/apostrophe/commit/7ca2d16237c72718ef7e5c7ae0458Patch
- https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-9mrh-v2v3-xExploitVendor Advisory
FAQ
What is CVE-2026-40186?
CVE-2026-40186 is a vulnerability with a CVSS score of 6.1 (MEDIUM). 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...
How severe is CVE-2026-40186?
CVE-2026-40186 has been rated MEDIUM with a CVSS base score of 6.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-40186?
Check the references section above for vendor advisories and patch information. Affected products include: Apostrophecms Apostrophecms, Apostrophecms Sanitize-Html.