GHSA-5V8H-3H3Q-446P

Vulnerability from github – Published: 2026-06-19 16:35 – Updated: 2026-06-19 16:35
VLAI
Summary
Nokogiri: Possible Use-After-Free when `Nokogiri::XML::Document#encoding=` raises an exception
Details

Summary

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.

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 pass an invalid encoding to Document#encoding=, rescue the resulting exception, and then continue using the same document. Nokogiri 1.19.4 makes this pattern safe with no change to the public API. The document no longer references freed memory after the exception is raised.

Mitigation

Upgrade to Nokogiri 1.19.4 or later.

If users are unable to upgrade, avoid passing attacker-controlled values to Document#encoding=. Applications that only assign developer-authored encodings are not directly exposed.

Credit

This issue was responsibly reported by Zheng Yu from depthfirst.com.

Severity
1.7 (Low)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U
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{
  "affected": [
    {
      "package": {
        "ecosystem": "RubyGems",
        "name": "nokogiri"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.19.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-416"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-19T16:35:58Z",
    "nvd_published_at": null,
    "severity": "LOW"
  },
  "details": "### Summary\n\nCalling `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\u0027s 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`.\n\nAffects the CRuby (libxml2) implementation only; JRuby is not affected.\n\n### Severity\n\nThe 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 pass an invalid encoding to `Document#encoding=`, rescue the resulting exception, and then continue using the same document. Nokogiri 1.19.4 makes this pattern safe with no change to the public API. The document no longer references freed memory after the exception is raised.\n\n### Mitigation\n\nUpgrade to Nokogiri 1.19.4 or later.\n\nIf users are unable to upgrade, avoid passing attacker-controlled values to `Document#encoding=`. Applications that only assign developer-authored encodings are not directly exposed.\n\n### Credit\n\nThis issue was responsibly reported by Zheng Yu from depthfirst.com.",
  "id": "GHSA-5v8h-3h3q-446p",
  "modified": "2026-06-19T16:35:58Z",
  "published": "2026-06-19T16:35:58Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/sparklemotion/nokogiri/security/advisories/GHSA-5v8h-3h3q-446p"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/sparklemotion/nokogiri"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Nokogiri: Possible Use-After-Free when `Nokogiri::XML::Document#encoding=` raises an exception"
}


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