CVE-2026-79771: Nokogiri Nokogiri XSLT Transform Has A Vulnerability

MODERATE
Advisory Identifier: GHSA-v2fc-qm4h-8hqv
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CVSS 5.3
CWE-401
Published
Advisory Summary

CVE-2026-79771 is a MODERATE (CVSS 5.3) nokogiri xslt transform has a vulnerability (CWE-401: Missing Release of Memory after Effective Lifetime) affecting Nokogiri libraries in the RubyGems ecosystem. The issue involves nokogiri xslt transform has a memory leak. Remediation is available by upgrading affected packages to version 1.19.3.

CVE-2026-79771 at a Glance

CVE Identifier CVE-2026-79771
GHSA Identifier GHSA-v2fc-qm4h-8hqv
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-401: Missing Release of Memory after Effective Lifetime
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:N/A:L).

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 None (I:N)
Availability Low (A:L)

How to Fix CVE-2026-79771

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: 1.19.3 
Upgrade nokogiri to 1.19.3
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-2026-79771, 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 1.19.3), 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-401: Missing Release of Memory after Effective Lifetime, where the product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse. 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 `Nokogiri::XSLT::Stylesheet#transform` leaks a small heap allocation when passed a Ruby string parameter containing a null byte. For applications that pass attacker-controlled input through `XSLT.transform` parameters, this may be a vector for a denial of service attack against long-running processes. ## Mitigation Upgrade to Nokogiri `>= 1.19.3`. Users may also be able to mitigate this issue without upgrading by validating untrusted transform parameters before passing them to `Nokogiri::XSLT::Stylesheet#transform`. ## Severity The Nokogiri maintainers have evaluated this as **Moderate Severity**, CVSS 5.3. Each leaked allocation is approximately 24–32 bytes, so meaningful memory growth requires sustained attacker-controlled traffic at high call rates. The bug does not cause memory corruption, information disclosure, or any change in the behavior of the transform itself, and the string-handling exception is raised as expected. Applications that do not pass raw attacker-controlled bytes to XSLT parameters are unlikely to be affected in practice. ## Resources - [CWE-401: Missing Release of Memory after Effective Lifetime](https://cwe.mitre.org/data/definitions/401.html) ## Credit This vulnerability was responsibly reported by @Captainjack-kor.

CVE-2026-79771 Affected Nokogiri Versions

1 component(s)
Fixed Versions:
1.19.3
Product / Package Ecosystem Affected Versions Fixed Version
nokogiri
gem/nokogiri
RubyGems
< 1.19.3
1.19.3

References

GitHub Advisory / Wiki ADVISORY
https://github.com/sparklemotion/nokogiri/security/advisories/GHSA-v2fc-qm4h-8hqv
NVD — CVE-2026-79771 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-79771
Nokogiri Source Repository REPOSITORY
https://github.com/sparklemotion/nokogiri
www.vulncheck.com/advisories/nokogiri... WEB
https://www.vulncheck.com/advisories/nokogiri-before-memory-leak-via-xslt-transform

Frequently Asked Questions

What is CVE-2026-79771?
CVE-2026-79771 is a security vulnerability in Nokogiri involving Nokogiri XSLT transform has a memory leak under CWE-401: Missing Release of Memory after Effective Lifetime.
Which Nokogiri versions are affected?
Affected versions include releases prior to 1.19.3 across affected packages: nokogiri.
What version fixes CVE-2026-79771?
Upgrading to 1.19.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is nokogiri affected?
Yes, nokogiri is affected in releases prior to 1.19.3. Upgrade your dependency to 1.19.3 or later.
What is the CVSS score of CVE-2026-79771?
CVE-2026-79771 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:N/A:L.
What CWE is associated with CVE-2026-79771?
CVE-2026-79771 is classified under CWE-401: Missing Release of Memory after Effective Lifetime (The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.).
How can I check RubyGems dependencies for CVE-2026-79771?
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-v2fc-qm4h-8hqv",
  "modified" : "2026-09-02T14:42:59Z",
  "published" : "2026-05-06T18:27:38Z",
  "aliases" : [ "CVE-2026-79771" ],
  "summary" : "Nokogiri XSLT transform has a memory leak",
  "details" : "## Summary\n\nNokogiri's `Nokogiri::XSLT::Stylesheet#transform` leaks a small heap allocation when passed a Ruby string parameter containing a null byte.\n\nFor applications that pass attacker-controlled input through `XSLT.transform` parameters, this may be a vector for a denial of service attack against long-running processes.\n\n\n## Mitigation\n\nUpgrade to Nokogiri `>= 1.19.3`.\n\nUsers may also be able to mitigate this issue without upgrading by validating untrusted transform parameters before passing them to `Nokogiri::XSLT::Stylesheet#transform`.\n\n\n## Severity\n\nThe Nokogiri maintainers have evaluated this as **Moderate Severity**, CVSS 5.3.\n\nEach leaked allocation is approximately 24–32 bytes, so meaningful memory growth requires sustained attacker-controlled traffic at high call rates. The bug does not cause memory corruption, information disclosure, or any change in the behavior of the transform itself, and the string-handling exception is raised as expected.\n\nApplications that do not pass raw attacker-controlled bytes to XSLT parameters are unlikely to be affected in practice.\n\n\n## Resources\n\n- [CWE-401: Missing Release of Memory after Effective Lifetime](https://cwe.mitre.org/data/definitions/401.html)\n\n\n## Credit\n\nThis vulnerability was responsibly reported by @Captainjack-kor.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "nokogiri"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.19.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/sparklemotion/nokogiri/security/advisories/GHSA-v2fc-qm4h-8hqv"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-79771"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/sparklemotion/nokogiri"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/nokogiri-before-memory-leak-via-xslt-transform"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-401" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-06T18:27:38Z",
    "nvd_published_at" : null
  }
}