GHSA-78cv-mqj4-43f7: Tornado Tornado Has Incomplete Validation Of Vulnerability

MODERATE
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CVSS 5.4
CWE-74
Published
Advisory Summary

GHSA-78cv-mqj4-43f7 is a MODERATE (CVSS 5.4) tornado has incomplete validation of vulnerability (CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')) affecting Tornado libraries in the PyPI ecosystem. The issue involves tornado has incomplete validation of cookie attributes. Remediation is available by upgrading affected packages to version 6.5.5.

GHSA-78cv-mqj4-43f7 at a Glance

CVE Identifier N/A
GHSA Identifier GHSA-78cv-mqj4-43f7
Severity MODERATE
CVSS v3.1 Base Score 5.4
CWE Classification CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
Affected Product Tornado
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 5.4

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:R/S:U/C:L/I:L/A:N).

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

How to Fix GHSA-78cv-mqj4-43f7

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

tornado fixed: 6.5.5 
pip install tornado>=6.5.5
Verify Direct and Transitive Dependencies

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

pip show tornado

How to Check if You Are Affected

To determine whether your Python environment is affected by GHSA-78cv-mqj4-43f7, inspect your installed packages using pip:

pip show tornado

Analyze the terminal output to locate any version of Tornado in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 6.5.5), your application is affected.

Note: The pip show tornado command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection'), where the product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component. In Tornado, 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

Values passed to the `domain`, `path`, and `samesite` arguments of `RequestHandler.set_cookie` were not completely validated in versions of Tornado prior to 6.5.5. In particular, semicolons would be allowed, which could be used to inject attacker-controlled values for other cookie attributes.

GHSA-78cv-mqj4-43f7 Affected Tornado Versions

1 component(s)
Fixed Versions:
6.5.5
Product / Package Ecosystem Affected Versions Fixed Version
tornado
pypi/tornado
PyPI
< 6.5.5
6.5.5

References

GitHub Advisory / Wiki ADVISORY
https://github.com/tornadoweb/tornado/security/advisories/GHSA-78cv-mqj4-43f7
Security Fix Commit FIX COMMIT
https://github.com/tornadoweb/tornado/commit/24a2d96ea115f663b223887deb0060f13974c104
Tornado Source Repository REPOSITORY
https://github.com/tornadoweb/tornado
Tornado Release RELEASE
https://github.com/tornadoweb/tornado/releases/tag/v6.5.5

Frequently Asked Questions

What is GHSA-78cv-mqj4-43f7?
GHSA-78cv-mqj4-43f7 is a security vulnerability in Tornado involving Tornado has incomplete validation of cookie attributes under CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection').
Which Tornado versions are affected?
Affected versions include releases prior to 6.5.5 across affected packages: tornado.
What version fixes GHSA-78cv-mqj4-43f7?
Upgrading to 6.5.5 (or the latest patched release for your respective branch) resolves the vulnerability.
Is tornado affected?
Yes, tornado is affected in releases prior to 6.5.5. Upgrade your dependency to 6.5.5 or later.
What is the CVSS score of GHSA-78cv-mqj4-43f7?
GHSA-78cv-mqj4-43f7 has a CVSS v3.1 base score of 5.4 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N.
What CWE is associated with GHSA-78cv-mqj4-43f7?
GHSA-78cv-mqj4-43f7 is classified under CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection') (The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.).
How can I check PyPI dependencies for GHSA-78cv-mqj4-43f7?
Run the dependency tree command: 'pip show tornado'. 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-78cv-mqj4-43f7",
  "modified" : "2026-03-11T22:17:00Z",
  "published" : "2026-03-11T22:17:00Z",
  "aliases" : [ ],
  "summary" : "Tornado has incomplete validation of cookie attributes",
  "details" : "Values passed to the `domain`, `path`, and `samesite` arguments of `RequestHandler.set_cookie` were not completely validated in versions of Tornado prior to 6.5.5. In particular, semicolons would be allowed, which could be used to inject attacker-controlled values for other cookie attributes.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "tornado"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "6.5.5"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 6.5.4"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/tornadoweb/tornado/security/advisories/GHSA-78cv-mqj4-43f7"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/tornadoweb/tornado/commit/24a2d96ea115f663b223887deb0060f13974c104"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/tornadoweb/tornado"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/tornadoweb/tornado/releases/tag/v6.5.5"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-74" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-11T22:17:00Z",
    "nvd_published_at" : null
  }
}