CVE-2026-79772: Nokogiri Nokogiri Does Not Check The Vulnerability

MODERATE
Advisory Identifier: GHSA-wx95-c6cv-8532
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CVSS 5.3
CWE-252
Published
Advisory Summary

CVE-2026-79772 is a MODERATE (CVSS 5.3) nokogiri does not check the vulnerability (CWE-252: Unchecked Return Value) affecting Nokogiri libraries in the RubyGems ecosystem. The issue involves nokogiri does not check the return value from xmlc14nexecute. Remediation is available by upgrading affected packages to version 1.19.1.

CVE-2026-79772 at a Glance

CVE Identifier CVE-2026-79772
GHSA Identifier GHSA-wx95-c6cv-8532
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-252: Unchecked Return Value
Affected Product Nokogiri
Package Ecosystem RubyGems
Published Date
Last Updated

Security Impact

CVSS: 5.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-79772

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: 1.19.1 
Upgrade nokogiri to 1.19.1
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 CVE-2026-79772, 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 1.19.1), 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-252: Unchecked Return Value, where the product does not check the return value from a method or function, which can prevent it from detecting unexpected states and conditions. 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's CRuby extension fails to check the return value from `xmlC14NExecute` in the method `Nokogiri::XML::Document#canonicalize` and `Nokogiri::XML::Node#canonicalize`. When canonicalization fails, an empty string is returned instead of raising an exception. This incorrect return value may allow downstream libraries to accept invalid or incomplete canonicalized XML, which has been demonstrated to enable signature validation bypass in SAML libraries. JRuby is not affected, as the Java implementation correctly raises `RuntimeError` on canonicalization failure. ## Mitigation Upgrade to Nokogiri `>= 1.19.1`. ## Severity The maintainers have assessed this as **Medium** severity. Nokogiri itself is a parsing library without a clear security boundary related to canonicalization, so the direct impact is that a method returns incorrect data on invalid input. However, this behavior was exploited in practice to bypass SAML signature validation in downstream libraries (see References). ## Credit This vulnerability was responsibly reported by HackerOne researcher `d4d`.

CVE-2026-79772 Affected Nokogiri Versions

1 component(s)
Fixed Versions:
1.19.1
Product / Package Ecosystem Affected Versions Fixed Version
nokogiri
gem/nokogiri
RubyGems
≥ 1.5.1
< 1.19.1
1.19.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/sparklemotion/nokogiri/security/advisories/GHSA-wx95-c6cv-8532
NVD — CVE-2026-79772 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-79772
Nokogiri Source Repository REPOSITORY
https://github.com/sparklemotion/nokogiri
www.vulncheck.com/advisories/nokogiri... WEB
https://www.vulncheck.com/advisories/nokogiri-before-unchecked-return-value-canonicalize

Frequently Asked Questions

What is CVE-2026-79772?
CVE-2026-79772 is a security vulnerability in Nokogiri involving Nokogiri does not check the return value from xmlC14NExecute under CWE-252: Unchecked Return Value.
Which Nokogiri versions are affected?
Affected versions include releases prior to 1.19.1 across affected packages: nokogiri.
What version fixes CVE-2026-79772?
Upgrading to 1.19.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is nokogiri affected?
Yes, nokogiri is affected in releases prior to 1.19.1. Upgrade your dependency to 1.19.1 or later.
What is the CVSS score of CVE-2026-79772?
CVE-2026-79772 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.
What CWE is associated with CVE-2026-79772?
CVE-2026-79772 is classified under CWE-252: Unchecked Return Value (The product does not check the return value from a method or function, which can prevent it from detecting unexpected states and conditions.).
How can I check RubyGems dependencies for CVE-2026-79772?
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-wx95-c6cv-8532",
  "modified" : "2026-09-02T14:42:33Z",
  "published" : "2026-02-18T21:57:38Z",
  "aliases" : [ "CVE-2026-79772" ],
  "summary" : "Nokogiri does not check the return value from xmlC14NExecute",
  "details" : "## Summary\n\nNokogiri's CRuby extension fails to check the return value from `xmlC14NExecute` in the method `Nokogiri::XML::Document#canonicalize` and `Nokogiri::XML::Node#canonicalize`. When canonicalization fails, an empty string is returned instead of raising an exception. This incorrect return value may allow downstream libraries to accept invalid or incomplete canonicalized XML, which has been demonstrated to enable signature validation bypass in SAML libraries.\n\nJRuby is not affected, as the Java implementation correctly raises `RuntimeError` on canonicalization failure.\n\n## Mitigation\n\nUpgrade to Nokogiri `>= 1.19.1`.\n\n## Severity\n\nThe maintainers have assessed this as **Medium** severity. Nokogiri itself is a parsing library without a clear security boundary related to canonicalization, so the direct impact is that a method returns incorrect data on invalid input. However, this behavior was exploited in practice to bypass SAML signature validation in downstream libraries (see References).\n\n## Credit\n\nThis vulnerability was responsibly reported by HackerOne researcher `d4d`.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "nokogiri"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.5.1"
      }, {
        "fixed" : "1.19.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/sparklemotion/nokogiri/security/advisories/GHSA-wx95-c6cv-8532"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-79772"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/sparklemotion/nokogiri"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/nokogiri-before-unchecked-return-value-canonicalize"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-252" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-02-18T21:57:38Z",
    "nvd_published_at" : null
  }
}