CVE-2026-57437
Nokogiri: Possible Use-After-Free when directly using `NokogirI::XML::XPathContext` beyond document lifetime
Blast Radius
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Description
Nokogiri is an open source XML and HTML library for the Ruby programming language. Prior to 1.19.4, 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. This vulnerability is fixed in 1.19.4.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | nokogiri | all versions | 1.19.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nokogiri. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update nokogiri to 1.19.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-57437 is resolved across your whole dependency graph.
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.
How O3 protects you
O3 pinpoints whether CVE-2026-57437 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-57437. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-57437 in your dependencies?
O3 detects CVE-2026-57437 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.