# CVE-2026-57436: Nokogiri: Possible Use-After-Free when setting `Document#root=` to an invalid node type

CVE-2026-57436 is fixed in ruby-nokogiri on 1 platform by DEBIAN-CVE-2026-57436 (version 1.19.4+dfsg-1), released July 3, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-57436
- Priority: Routine
- CVSS: 5.3 (Moderate)
- EPSS: 0.0040
- 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-2026-57436

## Description

Nokogiri is an open source XML and HTML library for the Ruby programming language. Prior to 1.19.4, Nokogiri::XML::Document#root= validated only that the new root was a Nokogiri::XML::Node, allowing a DTD node to be set as the document root. The result is a heap use-after-free during garbage collection or finalization, leading to an invalid memory read or potentially a segfault. 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-2026-57436](https://patchblox.com/security/data/fix/linux/debian-cve-2026-57436.md) | Jul 3, 2026 |

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Data as of 2026-11-09T01:18:40Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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