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TI-2026-74878 Aliases CVE-2026-104828

Mutation XSS in HtmlUnit Neko via TEXTAREA and TITLE serialization

Priority HIGH 71CWE-79Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Cross-site scripting
Confidentiality · integrity · availability
Low · Low · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-79.

Summary

The htmlunit-neko package from HtmlUnit is affected before 5.4.0. HTMLWriterFilter writes decoded TEXTAREA and TITLE content without entity encoding, so entity references are emitted as raw markup during a parse and serialize round trip (CWE-79). An unauthenticated remote attacker can turn encoded text into executable markup in applications that use it in an HTML sanitizer, content filter, or similar pipeline, when a browser renders the output.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Description from the CNA

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00324 25th percentileScored 2026-11-07
Fix Fixed htmlunit-neko (HtmlUnit): 5.4.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
HtmlUnithtmlunit-nekobefore 5.4.05.4.0Patch availableCNA
  • htmlunit-neko VendorHtmlUnit Affected before 5.4.0 Fixed in 5.4.0 Patch available CNA

Remediation

Upgrade htmlunit-neko to version 5.4.0, which fixes this issue.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

  • Fix · CNA htmlunit-neko (HtmlUnit) Fixed in 5.4.0

Timeline

  1. 2026-10-16 Threatist record created from CVE-2026-104828
  2. 2026-10-16 Priority changed: MEDIUM → LOW
  3. 2026-10-21 CISA SSVC decision points changed
  4. 2026-10-21 Priority changed: LOW → HIGH

References

Other 3

  • TI-2023-26758 HtmlUnit vulnerable to Remote Code Execution (RCE) via XSTL CVSS 3.1CRITICAL 9.8
  • TI-2023-11344 Code injection in net.sourceforge.htmlunit:htmlunit CVSS 3.1CRITICAL 9.8
  • TI-2020-04499 Code injection in HtmlUnit CVSS 3.1HIGH 8.1
  • TI-2022-11120 Certain Neko-related HTML parsers allow a denial of service via crafted Processing… CVSS 3.1HIGH 7.5
  • TI-2023-02621 Denial of service in HtmlUnit CVSS 3.1HIGH 7.5
  • TI-2022-12000 HtmlUnit NekoHtml Parser before 2.61.0 suffers from a denial of service vulnerability. CVSS 3.1HIGH 7.5

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences