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MEDIUM severity

CVE-2026-44664 — fast-xml-builder

MEDIUM

CVE-2026-44664 is a medium-severity (CVSS 6.1) CWE-91 vulnerability in fast-xml-builder. A fix is available for fast-xml-builder — see the affected versions and patch details below.

fast-xml-builder: Comment Value bypass regex

Also known asGHSA-45c6-75p6-83cc
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44664.

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs9th percentile — riskier than 9% of all scored CVEsHighest risk
0.00%0.25%0.50%0.75%0.0%0.2%Jun 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

83other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
fast-xml-buildernpm
72.0Mdownloads / week

Description

Summary

The fix for https://github.com/advisories/GHSA-gh4j-gqv2-49f6 in fast-xml-parser sanitizes -- sequences in XML comment content using .replace(/--/g, '- -'). This skip the values containing three consecutive dashes (e.g., --->...), allowing an attacker to break out of an XML comment and inject arbitrary XML/HTML content.

Impact

Any application with comment property enabled allow attacker to inject malicious or unwanted code like JS script tag in the XML/HTML output.

Workarounds

Check for the presence of 3 consecutive dashes externally in the property value used for comment tag.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmfast-xml-builder≥ 1.1.5&&< 1.1.61.1.6npm install fast-xml-builder@1.1.6

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fast-xml-builder, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update fast-xml-builder to 1.1.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44664 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

# Summary The fix for https://github.com/advisories/GHSA-gh4j-gqv2-49f6 in fast-xml-parser sanitizes `--` sequences in XML comment content using .replace(/--/g, '- -'). This skip the values containing three consecutive dashes (e.g., --->...), allowing an attacker to break out of an XML comment and inject arbitrary XML/HTML content. ### Impact Any application with comment property enabled allow attacker to inject malicious or unwanted code like JS script tag in the XML/HTML output. ### Workarounds Check for the presence of 3 consecutive dashes externally in the property value used for comment
O3 Security · Impact-Aware SCA

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CVE-2026-44664: fast-xml-builder — Fixed in 1.1.6