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High, CVSS 8.7amended

fast-xml-builder allows attribute values with unwanted quotes to bypass malicious or unwanted attributes

CVE-2026-44665GHSA-5wm8-gmm8-39j9

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (fast-xml-builder 1.1.7), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
8.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N · score source
EPSS
  • CVE-2026-44665: 0.24% estimated exploitation activity in the next 30 days; percentile 14.69 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary When an input data has quotes in attribute values but process entities is not enabled, it breaks the attribute value into multiple attributes. This gives the room for an attacker to insert unwanted attributes to the XML/HTML. Detail Malicious Input Output Workarounds If you're not ignoring attributes then keep processEntities flag true.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-5wm8-gmm8-39j9

  2. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 1 · created ·

    Published from osv record GHSA-5wm8-gmm8-39j9

Agent brief

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# Patch Next advisory brief: CVE-2026-44665

Advisory: fast-xml-builder allows attribute values with unwanted quotes to bypass malicious or unwanted attributes
IDs: CVE-2026-44665, GHSA-5wm8-gmm8-39j9
Record: https://patchnext.com/advisories/cve-2026-44665 (revision 3, source checked 26 Oct 2026, 12:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: fast-xml-builder 1.1.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm fast-xml-builder: affected <= 1.1.6; fixed in 1.1.7

## Suggested inspection (read-only)
- `npm ls fast-xml-builder --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on fast-xml-builder.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-5wm8-gmm8-39j9 (OSV record GHSA-5wm8-gmm8-39j9 lists affected ranges: npm fast-xml-builder >=0 <1.1.7 (fixed))
- Verified: https://github.com/advisories/GHSA-5wm8-gmm8-39j9 (GitHub-reviewed advisory GHSA-5wm8-gmm8-39j9 lists affected ranges: npm fast-xml-builder >=0 <=1.1.6)

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