{"id":"CVE-2026-21251","aliases":["EUVD-2026-7326","GHSA-6q2h-rrfg-fm75"],"status":"published","title":"Cluster Client Failover (CCF) Elevation of Privilege Vulnerability","description":"Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate privileges locally.","severity":{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00439,"percentile":0.38614,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-416"],"published":"2026-02-10T17:51:40Z","modified":"2026-08-19T16:26:10Z","products":[{"vendor":"microsoft","product":"windows server 2016"},{"vendor":"microsoft","product":"windows server 2016 (server core installation)"},{"vendor":"microsoft","product":"windows server 2019"},{"vendor":"microsoft","product":"windows server 2019 (server core installation)"},{"vendor":"microsoft","product":"windows server 2022"},{"vendor":"microsoft","product":"windows server 2022, 23h2 edition (server core installation)"},{"vendor":"microsoft","product":"windows server 2025"},{"vendor":"microsoft","product":"windows server 2025 (server core installation)"},{"vendor":"microsoft","product":"windows_server_2016"},{"vendor":"microsoft","product":"windows_server_2019"},{"vendor":"microsoft","product":"windows_server_2022"},{"vendor":"microsoft","product":"windows_server_2022_23h2"},{"vendor":"microsoft","product":"windows_server_2025"}],"references":[{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21251","tags":["vendor-advisory","patch","Vendor Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-21251"},{"url":"https://github.com/advisories/GHSA-6q2h-rrfg-fm75"}],"sources":{"cve":[{"id":"CVE-2026-21251","title":"Cluster Client Failover (CCF) Elevation of Privilege Vulnerability","description":"Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate privileges locally.","status":"published","published":"2026-02-10T17:51:40.939Z","modified":"2026-08-19T16:26:10.028Z","cvss":[{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C","level":"high","assessor":"cna"}],"cwes":["CWE-416"],"updated_at":"2026-11-02T13:41:42.05254Z"}],"euvd":[{"id":"EUVD-2026-7326","description":"Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate privileges locally.","status":"published","published":"2026-02-10T17:51:40Z","modified":"2026-08-19T16:26:10Z","cvss":[{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C","level":"high"}],"updated_at":"2026-11-02T18:01:44.172516Z"}],"ghsa":[{"id":"GHSA-6q2h-rrfg-fm75","title":"Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate...","description":"Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate privileges locally.","status":"published","published":"2026-02-10T18:30:41Z","modified":"2026-02-10T18:30:51Z","cvss":[{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-416"],"updated_at":"2026-11-02T15:06:07.875228Z"}],"nvd":[{"id":"CVE-2026-21251","description":"Use after free in Windows Cluster Client Failover allows an authorized attacker to elevate privileges locally.","status":"published","published":"2026-02-10T18:16:26.84Z","modified":"2026-06-17T10:18:22.083Z","cvss":[{"version":"3.1","score":7.8,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-416"],"updated_at":"2026-11-02T14:12:05.52517Z"}]}}