Nokogiri: Possible Use-After-Free when directly using `NokogirI::XML::XPathContext` beyond document lifetime (CVE-2026-57437) | HOL Guard CVE

Medium · CVSS 5.3CVE-2026-57437GHSA-P67V-3W7G-WJG7

Nokogiri: Possible Use-After-Free when directly using `NokogirI::XML::XPathContext` beyond document lifetime

Answer in brief

CVE-2026-57437 records a Medium severity (CVSS 5.3) vulnerability in Nokogiri: Possible Use-After-Free when directly using `NokogirI::XML::XPathContext` beyond document lifetime. The current sources do not mark it as known exploited. The current feed maps nokogiri (rubygems), nokogiri (rubygems). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jun 19, 2026Updated Sep 10, 2026Source checked Sep 10, 2026First seen by HOL Jun 19, 2026Material review Sep 10, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 5.3
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 5.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps nokogiri (rubygems), nokogiri (rubygems). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
nokogirirubygems	<1.19.4	1.19.4
nokogirirubygems	>=0 <1.19.4	1.19.4

Recommended response

Check inventory. Check lockfiles and deployed manifests for nokogiri, nokogiri.
Review the reported fix. Update nokogiri to 1.19.4; nokogiri to 1.19.4 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jun 19, 2026
Evidence: source:osv:source_dates:source-dates:record
Source modified
Sep 10, 2026
Evidence: source:osv:source_dates:source-dates:record
First seen by HOL
Jun 19, 2026

Sources and claim methodology

Upstream source description

### Summary `Nokogiri::XML::XPathContext` did not keep its source document alive for garbage collection. If an `XPathContext` outlived its document and the document was collected, evaluating an XPath expression could read invalid memory and potentially segfault. This is only reachable when application code constructs an `XPathContext` directly and lets the document become unreachable while continuing to use the context. The normal `Document#xpath`, `#css`, and related search methods are not affected, and it is not triggerable by malicious document input. Nokogiri 1.19.4 makes `XPathContext` keep its source document alive for as long as the context exists. Only the CRuby implementation is affected. 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 construct an `XML::XPathContext` directly and continue using it after allowing its source document to be garbage-collected. Nokogiri 1.19.4 makes this pattern safe with no change to the public API. The context now keeps its source document alive for as long as it exists. ### Mitigation Upgrade to Nokogiri 1.19.4 or later. As a workaround, ensure the source document remains referenced for as long as any `XPathContext` created from it is in use. The standard `Document#xpath`, `#css`, and related search methods already do this and are unaffected. ### Credit This issue was responsibly reported by Zheng Yu from depthfirst.com.

Quoted source text, attributed separately from HOL analysis.