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CVE-2026-57435

HIGH

Nokogiri is an open source XML and HTML library for the Ruby programming language. Prior to 1.19.4, Nokogiri’s CRuby native extension could leave a Ruby wrapper pointing to freed memory…

Published
Jun 25, 2026
Updated
Jun 26, 2026
Affected
0 pkgs
Patched
None yet
Exploits
None indexed

Description

Nokogiri is an open source XML and HTML library for the Ruby programming language. Prior to 1.19.4, Nokogiri’s CRuby native extension could leave a Ruby wrapper pointing to freed memory when replacing the value of an XML attribute. If Ruby code had already accessed an attribute child node, Nokogiri::XML::Attr#value= could free the underlying native child node while the wrapper remained reachable through the document node cache. A later use of the freed child node or a Ruby GC mark could dereference an invalid pointer, causing an invalid read and a possible segfault. This vulnerability is fixed in 1.19.4.

Affected Products

1 product · 1 configurations
Application
nokogirinokogiri
< 1.19.4
range

Detection & mitigation playbook

Vendor / appliance
  1. Detect

    Inventory every nokogiri nokogiri deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for exploitation at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.

  2. Fix

    Apply the nokogiri nokogiri security patch or hotfix for CVE-2026-57435 on the affected version, following the vendor advisory for your exact build.

  3. Workarounds

    Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.

  4. How O3 protects you

    O3 detects and blocks CVE-2026-57435 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.

Tailored to CVE-2026-57435. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

Nokogiri is an open source XML and HTML library for the Ruby programming language. Prior to 1.19.4, Nokogiri’s CRuby native extension could leave a Ruby wrapper pointing to freed memory when replacing the value of an XML attribute. If Ruby code had already accessed an attribute child node, Nokogiri::XML::Attr#value= could free the underlying native child node while the wrapper remained reachable through the document node cache. A later use of the freed child node or a Ruby GC mark could dereference an invalid pointer, causing an invalid read and a possible segfault. This vulnerability is fixed
O3 Security · Runtime Protection

Is CVE-2026-57435 being exploited in your environment?

O3's eBPF runtime sensors and L7 egress monitoring detect and block the CVE-2026-57435 exploit chain at execution — protecting unpatched and end-of-life systems until the vendor patch is applied.

CVE-2026-57435: Nokogiri Use After Free (High 7.5) | O3 Security