# CVE-2026-57236: Nokogiri: Possible Use-After-Free when `Nokogiri::XML::Document#encoding=` raises an exception

CVE-2026-57236 is fixed in ruby-nokogiri on 1 platform by DEBIAN-CVE-2026-57236 (version 1.19.4+dfsg-1), released July 3, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-57236
- Priority: High
- CVSS: 8.2 (Important)
- EPSS: 0.0043
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 25, 2026
- Weakness: Use After Free
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-57236

## Description

Nokogiri is an open source XML and HTML library for the Ruby programming language. Prior to 1.19.4, 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. This vulnerability is fixed in 1.19.4.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | ruby-nokogiri Debian 14 | 1.19.4+dfsg-1 | [DEBIAN-CVE-2026-57236](https://patchblox.com/security/data/fix/linux/debian-cve-2026-57236.md) | Jul 3, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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