Nokogiri: Possible Use-After-Free when Nokogiri::XML::Document#encoding= raises an exception

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

1.7 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U · score source

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary Calling Document#encoding= with an invalid encoding (e.g., a non-string, or a string containing a null byte) raises an exception, but only after freeing the document's current encoding string without replacing it. The document is left referencing freed memory, so the next call to Document#encoding reads invalid memory, which can cause a segfault or leak freed bytes into a Ruby String. Affects the CRuby (libxml2) implementation only; JRuby is not affected. Severity The Nokogiri maintainers have evaluated this as low severity. Reaching it requires an unusual API-usage pattern that does not arise during normal use. The application must pass an invalid encoding to Document#encoding=, rescue the resulting exception, and then continue using the same document. Nokogiri 1.19.4 makes this pattern safe with no change to the public API. The document no longer references freed memory after the exception is raised. Mitigation Upgrade to Nokogiri 1.19.4 or later. If users are unable to…

Published by the source

19 Jun 2026, 16:35 UTC

Last modified by the source

19 Jun 2026, 16:36 UTC

Source last checked

26 Oct 2026, 15:52 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-5v8h-3h3q-446p

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# Patch Next advisory brief: GHSA-5v8h-3h3q-446p

Advisory: Nokogiri: Possible Use-After-Free when `Nokogiri::XML::Document#encoding=` raises an exception
IDs: GHSA-5v8h-3h3q-446p
Record: https://patchnext.com/advisories/ghsa-5v8h-3h3q-446p (revision 1, source checked 26 Oct 2026, 15:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 1.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: nokogiri 1.19.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems nokogiri: affected < 1.19.4; fixed in 1.19.4

## Suggested inspection (read-only)
- RubyGems nokogiri: check the installed version with your package manager.

## 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 nokogiri.
- 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://github.com/advisories/GHSA-5v8h-3h3q-446p (GitHub-reviewed advisory GHSA-5v8h-3h3q-446p lists affected ranges: RubyGems nokogiri >=0 <1.19.4)

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