All vulnerabilities
CVE-2026-104828GHSA-39xg-prhf-8785

htmlunit-neko: HtmlUnit Neko: Mutation XSS (mXSS) in HTMLWriterFilter - TEXTAREA/TITLE entity decode without re-encode

HtmlUnit htmlunit-neko
Open in ThreatlineRecord JSON
CVSS
7.2High
ExploitationPublic exploit codeCISA's assessment says proof of concept code is public, assessed 21 Oct 2026. Not in the KEV catalogCISA via CVE List
Exploit odds (EPSS)0.26%Chance of exploitation activity in the next 30 days, higher than 17% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed inNone listedNo source names a fixed version. Check the vendor advisory below
Published15 Oct 2026Updated 21 Oct 2026CVE List

What fixes it

No source in this snapshot names a fixed version. The vendor advisories under References are the place to check.

Description

HtmlUnit Neko is an HtmlUnit adaptation of NekoHTML. Prior to 5.4.0, HTMLWriterFilter writes decoded TEXTAREA and TITLE character content without entity encoding because both elements are treated as special content. During a parse-and-serialize round trip, entity references inside these escapable raw-text elements are decoded by the parser and then emitted as raw markup by printCharacters(), changing the document's semantics. Applications that use htmlunit-neko in an HTML sanitizer, content filter, or other parse-transform-serialize pipeline can therefore turn attacker-controlled encoded text into executable markup when the output is rendered by a browser. This issue is fixed in version 5.4.0.

Text from CVE List

Affected versions 1

  • htmlunit-nekoaffected: < 5.4.0CVE List

References 3