CVE-2026-116538: XSS (CVSS 4.7)

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.

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CVSS v3.1 Score

4.7

MEDIUM

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

EPSS — Exploit Prediction

0.0029

Probability of exploitation

0.21%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-79 Cross-site Scripting (XSS)

References

Other References

https://github.com/mganss/HtmlSanitizer https://github.com/mganss/HtmlSanitizer/blob/v9.2.995/src/HtmlSanitizer/HtmlSanitizer.cs#L456-L465 https://github.com/mganss/HtmlSanitizer/blob/v9.2.995/src/HtmlSanitizer/HtmlSanitizer.cs#L555-L583 https://github.com/mganss/HtmlSanitizer/commit/96afbc818e64de7571ea17954a05d523e819c56f https://github.com/mganss/HtmlSanitizer/commit/ab626e7a4f2893f7e9ec0a72779ae19c5ec439a7 https://github.com/mganss/HtmlSanitizer/releases/tag/v10.0.1037-beta https://github.com/mganss/HtmlSanitizer/releases/tag/v9.2.1039 https://joshua.hu/htmlsanitizer-sanitizedom-body-html-attribute-bypass https://www.vulncheck.com/advisories/htmlsanitizer-before-9.2.1039-xss-via-sanitizedom-body-and-html-attributes

Frequently Asked Questions

What is CVE-2026-116538? +

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. It has a CVSS v3.1 base score of 4.7 (MEDIUM).

How severe is CVE-2026-116538? +

CVE-2026-116538 has a CVSS v3.1 score of 4.7 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0029, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-116538? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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