GHSA-WJV4-X9W8-WM3H
Vulnerability from github – Published: 2026-06-19 16:36 – Updated: 2026-06-19 16:36Summary
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.
{
"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": "2026-06-19T16:36:59Z",
"nvd_published_at": null,
"severity": "LOW"
},
"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.",
"id": "GHSA-wjv4-x9w8-wm3h",
"modified": "2026-06-19T16:36:59Z",
"published": "2026-06-19T16:36:59Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/sparklemotion/nokogiri/security/advisories/GHSA-wjv4-x9w8-wm3h"
},
{
"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 setting `Document#root=` to an invalid node type"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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