{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "6.5.5"
              },
              {
                "fixed": "6.5.8"
              },
              {
                "introduced": "0"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "DESCRIPTION"
            ]
          },
          "events": [
            {
              "introduced": "7d6465056ceb7a054b3f64cf1c18271753b10482"
            },
            {
              "fixed": "a55abe3e3bf59994f29b2f7084c46341f0d4f6a7"
            }
          ],
          "repo": "https://github.com/tornadoweb/tornado",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-wwv5-g3v4-889x"
  ],
  "database_specific": {
    "cna_assigner": "VulnCheck",
    "cwe_ids": [
      "CWE-113"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/91xxx/CVE-2026-91991.json"
  },
  "details": "Tornado before 6.5.8 contains an incomplete fix for cookie attribute injection that allows attackers to inject arbitrary cookie attributes by passing capitalized or legacy keyword arguments to set_cookie. Attackers can embed semicolon-delimited data in capitalized parameters like Domain, Path, or SameSite to bypass validation and modify cookie security attributes.",
  "id": "CVE-2026-91991",
  "modified": "2026-09-17T03:30:37.336658528Z",
  "published": "2026-09-15T15:18:32.408Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/91xxx/CVE-2026-91991.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-wwv5-g3v4-889x"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-91991"
    },
    {
      "type": "ADVISORY",
      "url": "https://www.vulncheck.com/advisories/tornado-before-6.5.8-cookie-attribute-injection-via-capitalized-kwargs"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Tornado before 6.5.8 Cookie Attribute Injection via Capitalized kwargs"
}