ubuntu-cve-2026-31958
Vulnerability from osv_ubuntu
Published
2026-03-11 20:16
Modified
2026-05-20 15:27
Summary
Details

Tornado is a Python web framework and asynchronous networking library. In versions of Tornado prior to 6.5.5, the only limit on the number of parts in multipart/form-data is the max_body_size setting (default 100MB). Since parsing occurs synchronously on the main thread, this creates the possibility of denial-of-service due to the cost of parsing very large multipart bodies with many parts. This vulnerability is fixed in 6.5.5.

Severity
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
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+esm3"
          },
          {
            "binary_name": "python3-tornado",
            "binary_version": "4.2.1-1ubuntu3.1+esm3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:16.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@4.2.1-1ubuntu3.1+esm3?arch=source\u0026distro=esm-infra/xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.2.1-1ubuntu3.1+esm3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.2.1-1ubuntu2",
        "4.2.1-1ubuntu3",
        "4.2.1-1ubuntu3.1",
        "4.2.1-1ubuntu3.1+esm1",
        "4.2.1-1ubuntu3.1+esm2"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
        "binaries": [
          {
            "binary_name": "python-tornado",
            "binary_version": "4.5.3-1ubuntu0.2+esm3"
          },
          {
            "binary_name": "python3-tornado",
            "binary_version": "4.5.3-1ubuntu0.2+esm3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:18.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@4.5.3-1ubuntu0.2+esm3?arch=source\u0026distro=esm-apps/bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.5.3-1ubuntu0.2+esm3"
            }
          ],
          "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",
        "4.5.3-1ubuntu0.2+esm2"
      ]
    },
    {
      "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~esm5"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:20.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@6.0.3+really5.1.1-3ubuntu0.1~esm5?arch=source\u0026distro=esm-apps/focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.0.3+really5.1.1-3ubuntu0.1~esm5"
            }
          ],
          "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",
        "6.0.3+really5.1.1-3ubuntu0.1~esm3"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
        "binaries": [
          {
            "binary_name": "python3-tornado",
            "binary_version": "6.1.0-3ubuntu0.1~esm5"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:22.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@6.1.0-3ubuntu0.1~esm5?arch=source\u0026distro=esm-apps/jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.1.0-3ubuntu0.1~esm5"
            }
          ],
          "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",
        "6.1.0-3ubuntu0.1~esm4"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "python3-tornado",
            "binary_version": "6.4.0-1ubuntu0.5"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@6.4.0-1ubuntu0.5?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.4.0-1ubuntu0.5"
            }
          ],
          "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",
        "6.4.0-1ubuntu0.4"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "python3-tornado",
            "binary_version": "6.4.2-3ubuntu0.3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:25.10",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@6.4.2-3ubuntu0.3?arch=source\u0026distro=questing"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.4.2-3ubuntu0.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "6.4.2-1",
        "6.4.2-2",
        "6.4.2-2ubuntu1",
        "6.4.2-3",
        "6.4.2-3ubuntu0.2"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "python3-tornado",
            "binary_version": "6.5.4-0.1ubuntu0.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@6.5.4-0.1ubuntu0.1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.5.4-0.1ubuntu0.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "6.4.2-3",
        "6.5.2-3",
        "6.5.4-0.1"
      ]
    }
  ],
  "aliases": [],
  "details": "Tornado is a Python web framework and asynchronous networking library. In versions of Tornado prior to 6.5.5, the only limit on the number of parts in multipart/form-data is the max_body_size setting (default 100MB). Since parsing occurs synchronously on the main thread, this creates the possibility of denial-of-service due to the cost of parsing very large multipart bodies with many parts. This vulnerability is fixed in 6.5.5.",
  "id": "UBUNTU-CVE-2026-31958",
  "modified": "2026-05-20T15:27:20Z",
  "published": "2026-03-11T20:16:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-31958"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-31958"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-qjxf-f2mg-c6mc"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-8198-1"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-8198-2"
    }
  ],
  "related": [
    "USN-8198-1",
    "USN-8198-2"
  ],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    },
    {
      "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-2026-31958"
  ]
}



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