{"id":"CVE-2026-103261","title":"Tornado before 6.5.9 fails to limit the number of query string fields in HTTPServerRequest.__init__, allowing remote attackers to cause event-loop stalling by sending requests with thousands of query parameters","summary":"Tornado before 6.5.9 fails to limit the number of query string fields in HTTPServerRequest.__init__, allowing remote attackers to cause event-loop stalling by sending requests with thousands of query parameters. Attackers can send unauth…","severity":"medium","cvss":5.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","cwe":["CWE-770"],"vendor":"tornadoweb","product":"tornado","affected":["tornado < 6.5.9"],"published":"2026-10-01","updated":"2026-10-01","sourceUpdated":"2026-10-01T15:17:26.580","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-103261","references":[{"url":"https://github.com/tornadoweb/tornado/commit/03945136ea9746eccf61caf88edae39642e59c93","label":"disclosure@vulncheck.com"},{"url":"https://github.com/tornadoweb/tornado/security/advisories/GHSA-3hv7-mjh2-fv65","label":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/tornado-before-6.5.9-denial-of-service-via-query-string","label":"disclosure@vulncheck.com"},{"url":"https://github.com/tornadoweb/tornado/pull/3719"},{"url":"https://github.com/tornadoweb/tornado/commit/8a61dd6005f42733015160f3c23a2bcffe200542"},{"url":"https://github.com/tornadoweb/tornado"},{"url":"https://github.com/tornadoweb/tornado/releases/tag/v6.5.9"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-103261.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-103261"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2544529"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-103261"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-103261"}],"tags":["nvd","cve.org","osv","pip","csaf","vex","red-hat"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-10-01T14:44:15.608259Z"},"ingestedAt":"2026-10-01T11:42:53.804Z","aliases":["GHSA-3hv7-mjh2-fv65"],"ecosystem":"pip","patched":["tornado 6.5.9"],"epss":0.00467,"epssPercentile":0.40263,"slug":"CVE-2026-103261","body":"## Overview\n\nTornado before 6.5.9 fails to limit the number of query string fields in HTTPServerRequest.__init__, allowing remote attackers to cause event-loop stalling by sending requests with thousands of query parameters. Attackers can send unauthenticated GET requests with unbounded query-string field counts to degrade response times for all clients sharing the same IOLoop.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Package advisory (CVE-2026-103261)\n\nAffected packages:\n\n- `tornado < 6.5.9`\n\nPatched in:\n\n- `tornado 6.5.9`\n\nSource: https://osv.dev/vulnerability/GHSA-3hv7-mjh2-fv65\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Lightspeed Core, Migration Toolkit for Applications 8, OpenShift Lightspeed, Red Hat Ansible Automation Platform 2, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, … · no fix planned: Migration Toolkit for Applications 8, Red Hat OpenStack Platform 16.2, Red Hat OpenStack Platform 17.1, Lightspeed Core, … · updated 2026-10-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-103261.json)","depth":"sunlit","depthScore":29,"depthScoreParts":{"impact":29.2,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}