GHSA-wjv4-x9w8-wm3h: Nokogiri Possible Use-After-Free When Setting `Document#root=` Vulnerability

LOW
Share
CWE-416
Published
Advisory Summary

GHSA-wjv4-x9w8-wm3h is a LOW possible use-after-free when setting `document#root=` vulnerability (CWE-416: Use After Free) affecting Nokogiri libraries in the RubyGems ecosystem. The issue involves possible use-after-free when setting `document#root=` to an invalid node type. Remediation is available by upgrading affected packages to version 1.19.4.

GHSA-wjv4-x9w8-wm3h at a Glance

CVE Identifier N/A
GHSA Identifier GHSA-wjv4-x9w8-wm3h
Severity LOW
CVSS v3.1 Base Score N/A
CWE Classification CWE-416: Use After Free
Affected Product Nokogiri
Package Ecosystem RubyGems
Published Date
Last Updated

How to Fix GHSA-wjv4-x9w8-wm3h

To remediate this vulnerability, upgrade all affected Nokogiri dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

nokogiri fixed: 1.19.4 
Upgrade nokogiri to 1.19.4
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for nokogiri

How to Check if You Are Affected

To determine whether your application is affected by GHSA-wjv4-x9w8-wm3h, inspect your project dependencies for Nokogiri:

inspect dependencies for nokogiri

Analyze the terminal output to locate any version of Nokogiri in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.19.4), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-416: Use After Free, where the product reuses or references memory after it has been freed. at some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer. In Nokogiri, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary `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. Nokogiri 1.19.4 restricts `Document#root=` to element nodes, raising `TypeError` for any other node type. This memory-safety issue affects only the CRuby implementation (libxml2). The JRuby implementation was not affected; the same input validation was added there for behavioral parity. ### Severity The Nokogiri maintainers have evaluated this as low severity. This is only triggered by a programming error. It requires application code to assign a non-element node such as a DTD as the document root via `Document#root=`. Nokogiri 1.19.4 now raises `TypeError` instead of allowing a use-after-free. It cannot be triggered by untrusted input or through normal use of the public API. ### Mitigation Upgrade to Nokogiri 1.19.4 or later. As a workaround, applications that cannot upgrade should avoid assigning a DTD (or any non-element node) via `Document#root=`. ### Credit This issue was responsibly reported by Zheng Yu from depthfirst.com.

GHSA-wjv4-x9w8-wm3h Affected Nokogiri Versions

1 component(s)
Fixed Versions:
1.19.4
Product / Package Ecosystem Affected Versions Fixed Version
nokogiri
gem/nokogiri
RubyGems
< 1.19.4
1.19.4

References

GitHub Advisory / Wiki ADVISORY
https://github.com/sparklemotion/nokogiri/security/advisories/GHSA-wjv4-x9w8-wm3h
Nokogiri Source Repository REPOSITORY
https://github.com/sparklemotion/nokogiri

Frequently Asked Questions

What is GHSA-wjv4-x9w8-wm3h?
GHSA-wjv4-x9w8-wm3h is a security vulnerability in Nokogiri involving Possible Use-After-Free when setting `Document#root=` to an invalid node type under CWE-416: Use After Free.
Which Nokogiri versions are affected?
Affected versions include releases prior to 1.19.4 across affected packages: nokogiri.
What version fixes GHSA-wjv4-x9w8-wm3h?
Upgrading to 1.19.4 (or the latest patched release for your respective branch) resolves the vulnerability.
Is nokogiri affected?
Yes, nokogiri is affected in releases prior to 1.19.4. Upgrade your dependency to 1.19.4 or later.
What CWE is associated with GHSA-wjv4-x9w8-wm3h?
GHSA-wjv4-x9w8-wm3h is classified under CWE-416: Use After Free (The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.).
How can I check RubyGems dependencies for GHSA-wjv4-x9w8-wm3h?
Run the dependency tree command: 'inspect dependencies for nokogiri'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-wjv4-x9w8-wm3h",
  "modified" : "2026-06-19T16:36:59Z",
  "published" : "2026-06-19T16:36:59Z",
  "aliases" : [ ],
  "summary" : "Nokogiri: Possible Use-After-Free when setting `Document#root=` to an invalid node type",
  "details" : "### Summary\n\n`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.\n\nNokogiri 1.19.4 restricts `Document#root=` to element nodes, raising `TypeError` for any other node type.\n\nThis memory-safety issue affects only the CRuby implementation (libxml2). The JRuby implementation was not affected; the same input validation was added there for behavioral parity.\n\n### Severity\n\nThe Nokogiri maintainers have evaluated this as low severity. This is only triggered by a programming error. It requires application code to assign a non-element node such as a DTD as the document root via `Document#root=`. Nokogiri 1.19.4 now raises `TypeError` instead of allowing a use-after-free. It cannot be triggered by untrusted input or through normal use of the public API.\n\n### Mitigation\n\nUpgrade to Nokogiri 1.19.4 or later.\n\nAs a workaround, applications that cannot upgrade should avoid assigning a DTD (or any non-element node) via `Document#root=`.\n\n### Credit\n\nThis issue was responsibly reported by Zheng Yu from depthfirst.com.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "nokogiri"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.19.4"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/sparklemotion/nokogiri/security/advisories/GHSA-wjv4-x9w8-wm3h"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/sparklemotion/nokogiri"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-416" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-19T16:36:59Z",
    "nvd_published_at" : null
  }
}