Vulnerability · Published Oct 26, 2026 · Assigned by VulnCheck

CVE-2026-116538HtmlSanitizer before 9.2.1039 XSS via SanitizeDom Body and HTML Attributes

Medium 4.7

In plain English

A medium-severity cross-site scripting in HtmlSanitizer from mganss. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 21% of all known vulnerabilities).

Severity (CVSS 3.1)4.7Medium

Exploit odds (30 days)0.3%top 78.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

HtmlSanitizer before 9.2.1039 and 10.0 prereleases before 10.0.1037-beta contains a cross-site scripting vulnerability because SanitizeDom(string) never sanitizes attributes on the html and body wrapper elements. Attackers can supply input with a second body or html tag carrying event handlers like onload, executing script when applications render serialized document or body outer HTML.

Affected products (as reported)

Vendor	Product	Versions
mganss	HtmlSanitizer	0 – before 9.2.103910.0.0-beta – before 10.0.1037-beta

Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N

References

Patch Commit patch
https://github.com/mganss/HtmlSanitizer/commit/ab626e7a4f2893f7e9ec0a72779ae19c5ec439a7 patch
https://github.com/mganss/HtmlSanitizer/blob/v9.2.995/src/HtmlSanitizer/HtmlSanitizer.cs#L456-L465 technical-description
https://github.com/mganss/HtmlSanitizer/blob/v9.2.995/src/HtmlSanitizer/HtmlSanitizer.cs#L555-L583 technical-description
https://joshua.hu/htmlsanitizer-sanitizedom-body-html-attribute-bypass technical-description
HtmlSanitizer v9.2.1039 Release Notes release-notes
HtmlSanitizer v10.0.1037-beta Release Notes release-notes
https://github.com/mganss/HtmlSanitizer product
VulnCheck Advisory: HtmlSanitizer before 9.2.1039 XSS via SanitizeDom Body and HTML Attributes third-party-advisory