{"id":"CVE-2025-67726","title":"Tornado is a Python web framework and asynchronous networking library","summary":"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.…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-400","CWE-834","CWE-1333"],"vendor":"tornadoweb","product":"tornado","affected":["tornado < 6.5.3"],"patched":["tornado 6.5.3"],"published":"2025-12-12","updated":"2026-10-07","sourceUpdated":"2026-10-07T20:10:01.970","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2025-67726","references":[{"url":"https://github.com/tornadoweb/tornado/commit/771472cfdaeebc0d89a9cc46e249f8891a6b29cd","label":"security-advisories@github.com"},{"url":"https://github.com/tornadoweb/tornado/releases/tag/v6.5.3","label":"security-advisories@github.com"},{"url":"https://github.com/tornadoweb/tornado/security/advisories/GHSA-jhmp-mqwm-3gq8","label":"security-advisories@github.com"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-67726.json"},{"url":"https://access.redhat.com/security/cve/CVE-2025-67726"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2421733"},{"url":"https://www.cve.org/CVERecord?id=CVE-2025-67726"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2025-67726"},{"url":"https://access.redhat.com/errata/RHSA-2026:0930"},{"url":"https://access.redhat.com/errata/RHSA-2026:2462"},{"url":"https://access.redhat.com/errata/RHSA-2026:2469"},{"url":"https://access.redhat.com/errata/RHSA-2026:2465"},{"url":"https://access.redhat.com/errata/RHSA-2026:2484"},{"url":"https://access.redhat.com/errata/RHSA-2026:2106"},{"url":"https://access.redhat.com/errata/RHSA-2026:3713"}],"tags":["nvd","osv","pip","csaf","vex","red-hat","score-dispute"],"epss":0.00535,"epssPercentile":0.44976,"aliases":["PYSEC-2025-267","GHSA-jhmp-mqwm-3gq8"],"ecosystem":"pip","ingestedAt":"2026-07-13T18:58:06.943Z","scores":{"nvd":7.5,"vendor":5.3},"slug":"CVE-2025-67726","body":"## Overview\n\nTornado 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.\n\n## Affected\n\n- `tornado < 6.5.3`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `tornado 6.5.3`\n\n## Package advisory (CVE-2025-67726)\n\nAffected packages:\n\n- `tornado < 6.5.3`\n\nPatched in:\n\n- `tornado 6.5.3`\n\nSource: https://osv.dev/vulnerability/PYSEC-2025-267\n\n## Vendor advisories\n\n- **RHSA-2026:0930** · Red Hat · fixed in: Red Hat Enterprise Linux HighAvailability (v. 8), Red Hat Enterprise Linux ResilientStorage (v. 8) · released 2026-01-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:0930)\n- **RHSA-2026:2462** · Red Hat · fixed in: Red Hat Enterprise Linux High Availability AUS (v.8.4), Red Hat Enterprise Linux HighAvailability EUS EXTENSION (v.8.4) · released 2026-02-10 · [advisory](https://access.redhat.com/errata/RHSA-2026:2462)\n- **RHSA-2026:2469** · Red Hat · fixed in: Red Hat Enterprise Linux High Availability E4S (v.8.6), Red Hat Enterprise Linux High Availability TUS (v.8.6) · released 2026-02-10 · [advisory](https://access.redhat.com/errata/RHSA-2026:2469)\n- **RHSA-2026:2465** · Red Hat · fixed in: Red Hat Enterprise Linux High Availability E4S (v.8.8), Red Hat Enterprise Linux High Availability TUS (v.8.8) · released 2026-02-10 · [advisory](https://access.redhat.com/errata/RHSA-2026:2465)\n- **RHSA-2026:2484** · Red Hat · fixed in: Red Hat Enterprise Linux High Availability E4S (v.9.0), Red Hat Enterprise Linux ResilientStorage E4S (v.9.0) · released 2026-02-10 · [advisory](https://access.redhat.com/errata/RHSA-2026:2484)\n- **RHSA-2026:2106** · Red Hat · fixed in: Red Hat OpenShift AI 2.25 · released 2026-02-05 · [advisory](https://access.redhat.com/errata/RHSA-2026:2106)\n- **RHSA-2026:3713** · Red Hat · fixed in: Red Hat OpenShift AI 3.3 · released 2026-03-04 · [advisory](https://access.redhat.com/errata/RHSA-2026:3713)\n- **Red Hat VEX** · Moderate · affected: external secrets operator for Red Hat OpenShift - Tech Preview, Red Hat Advanced Cluster Security 4, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat Enterprise Linux AI (RHEL AI) 3 · no fix planned: external secrets operator for Red Hat OpenShift - Tech Preview, Red Hat Advanced Cluster Security 4, Red Hat Enterprise Linux AI (RHEL AI) 3, Red Hat Enterprise Linux 10, … · updated 2026-10-09 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-67726.json)","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}