ubuntu-cve-2025-67726
Vulnerability from osv_ubuntu
Published
2025-12-12 07:15
Modified
2026-01-20 05:33
Summary
Details

Tornado is a Python web framework and asynchronous networking library. Versions 6.5.2 and below use an inefficient algorithm when parsing parameters for HTTP header values, potentially causing a DoS. The _parseparam function in httputil.py is used to parse specific HTTP header values, such as those in multipart/form-data and repeatedly calls string.count() within a nested loop while processing quoted semicolons. 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. This issue is fixed in version 6.5.3.

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

{
  "affected": [
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro",
        "binaries": [
          {
            "binary_name": "python-tornado",
            "binary_version": "4.2.1-1ubuntu3.1+esm2"
          },
          {
            "binary_name": "python3-tornado",
            "binary_version": "4.2.1-1ubuntu3.1+esm2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:16.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@4.2.1-1ubuntu3.1+esm2?arch=source\u0026distro=esm-infra/xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.2.1-1ubuntu3.1+esm2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.2.1-1ubuntu2",
        "4.2.1-1ubuntu3",
        "4.2.1-1ubuntu3.1",
        "4.2.1-1ubuntu3.1+esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
        "binaries": [
          {
            "binary_name": "python-tornado",
            "binary_version": "4.5.3-1ubuntu0.2+esm2"
          },
          {
            "binary_name": "python3-tornado",
            "binary_version": "4.5.3-1ubuntu0.2+esm2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:18.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@4.5.3-1ubuntu0.2+esm2?arch=source\u0026distro=esm-apps/bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.5.3-1ubuntu0.2+esm2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.5.1-2.1~build2",
        "4.5.2-1",
        "4.5.3-1",
        "4.5.3-1ubuntu0.1",
        "4.5.3-1ubuntu0.2",
        "4.5.3-1ubuntu0.2+esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
        "binaries": [
          {
            "binary_name": "python3-tornado",
            "binary_version": "6.0.3+really5.1.1-3ubuntu0.1~esm3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:20.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@6.0.3+really5.1.1-3ubuntu0.1~esm3?arch=source\u0026distro=esm-apps/focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.0.3+really5.1.1-3ubuntu0.1~esm3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "5.1.1-4ubuntu1",
        "5.1.1-4ubuntu5",
        "6.0.3+really5.1.1-2",
        "6.0.3+really5.1.1-2build1",
        "6.0.3+really5.1.1-2build2",
        "6.0.3+really5.1.1-3",
        "6.0.3+really5.1.1-3ubuntu0.1~esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
        "binaries": [
          {
            "binary_name": "python3-tornado",
            "binary_version": "6.1.0-3ubuntu0.1~esm4"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:22.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@6.1.0-3ubuntu0.1~esm4?arch=source\u0026distro=esm-apps/jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.1.0-3ubuntu0.1~esm4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "6.1.0-1build1",
        "6.1.0-2",
        "6.1.0-3",
        "6.1.0-3build1",
        "6.1.0-3ubuntu0.1~esm1",
        "6.1.0-3ubuntu0.1~esm2"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "python3-tornado",
            "binary_version": "6.4.0-1ubuntu0.4"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@6.4.0-1ubuntu0.4?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.4.0-1ubuntu0.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "6.3.2-1",
        "6.4.0-0ubuntu1",
        "6.4.0-1",
        "6.4.0-1build1",
        "6.4.0-1ubuntu0.1",
        "6.4.0-1ubuntu0.2"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "python3-tornado",
            "binary_version": "6.4.2-3ubuntu0.2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:25.10",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@6.4.2-3ubuntu0.2?arch=source\u0026distro=questing"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.4.2-3ubuntu0.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "6.4.2-1",
        "6.4.2-2",
        "6.4.2-2ubuntu1",
        "6.4.2-3"
      ]
    }
  ],
  "aliases": [],
  "details": "Tornado is a Python web framework and asynchronous networking library. Versions 6.5.2 and below use an inefficient algorithm when parsing parameters for HTTP header values, potentially causing a DoS. The _parseparam function in httputil.py is used to parse specific HTTP header values, such as those in multipart/form-data and repeatedly calls string.count() within a nested loop while processing quoted semicolons. 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. This issue is fixed in version 6.5.3.",
  "id": "UBUNTU-CVE-2025-67726",
  "modified": "2026-01-20T05:33:15Z",
  "published": "2025-12-12T07:15:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2025-67726"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-67726"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-jhmp-mqwm-3gq8"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/tornadoweb/tornado/commit/771472cfdaeebc0d89a9cc46e249f8891a6b29cd"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/tornadoweb/tornado/releases/tag/v6.5.3"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-7950-1"
    }
  ],
  "related": [
    "USN-7950-1"
  ],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2025-67726"
  ]
}



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