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brew-jupyterlab-cve-2025-67726
Vulnerability from osv_homebrew
Published
2026-08-13 17:01
Modified
2026-09-16 09:21
Summary
Tornado: Quadratic DoS via Crafted Multipart Parameters
Details

Summary

The _parseparam function in Tornado's httputil.py is used to parse specific HTTP header values, such as those in multipart/form-data. This function uses an inefficient algorithm that repeatedly calls string.count() within a nested loop while processing quoted semicolons (e.g., param=";").

As a result, if an attacker sends a request with a large number of maliciously crafted parameters in a Content-Disposition header, the server's CPU usage increases quadratically (O(n²)) during parsing. Due to Tornado's single event loop architecture, a single malicious request can cause the entire server to become unresponsive for an extended period, leading to a Denial of Service (DoS).

Severity: High

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "tornado",
        "resource_purl": "pkg:pypi/tornado@6.5.9",
        "upstream_fixed_in": "6.5.3"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "jupyterlab",
        "purl": "pkg:brew/jupyterlab"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.6.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/tornado@6.5.9",
        "name": "tornado",
        "resource": "tornado",
        "strategy": "registry",
        "subject_version": "6.5.9"
      }
    ]
  },
  "details": "## Summary\n\nThe `_parseparam` function in Tornado\u0027s `httputil.py` is used to parse specific HTTP header values, such as those in `multipart/form-data`. This function uses an inefficient algorithm that repeatedly calls `string.count()` within a nested loop while processing quoted semicolons (e.g., `param=\";\"`).\n\nAs a result, if an attacker sends a request with a large number of maliciously crafted parameters in a `Content-Disposition` header, the server\u0027s CPU usage increases quadratically (O(n\u00b2)) during parsing. Due to Tornado\u0027s single event loop architecture, a single malicious request can cause the entire server to become unresponsive for an extended period, leading to a Denial of Service (DoS).\n\n**Severity: High**",
  "id": "BREW-jupyterlab-CVE-2025-67726",
  "modified": "2026-09-16T09:21:00Z",
  "published": "2026-08-13T17:01:18Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-jhmp-mqwm-3gq8"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-67726"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/commit/771472cfdaeebc0d89a9cc46e249f8891a6b29cd"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/tornado/PYSEC-2025-267.yaml"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/tornadoweb/tornado"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/releases/tag/v6.5.3"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Tornado: Quadratic DoS via Crafted Multipart Parameters",
  "upstream": [
    "GHSA-jhmp-mqwm-3gq8",
    "CVE-2025-67726",
    "PYSEC-2025-267"
  ]
}



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