{"id":"CVE-2021-22991","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-22991","generatedAt":"2026-10-31T15:09:27.901Z","title":"F5 BIG-IP Traffic Management Microkernel Buffer Overflow","description":"On BIG-IP versions 16.0.x before 16.0.1.1, 15.1.x before 15.1.2.1, 14.1.x before 14.1.4, 13.1.x before 13.1.3.6, and 12.1.x before 12.1.5.3, undisclosed requests to a virtual server may be incorrectly handled by the Traffic Management Microkernel (TMM) URI normalization, which may trigger a buffer overflow, resulting in a DoS attack. In certain situations, it may theoretically allow bypass of URL based access control or remote code execution (RCE). Note: Software versions which have reached End of Software Development (EoSD) are not evaluated.","published":"2021-03-31T18:15:15.000Z","lastModified":"2026-06-17T03:38:10.000Z","status":"Analyzed","sourceIdentifier":"f5sirt@f5.com","cvss":{"version":"3.1","score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"cwe":["CWE-119"],"affected":["f5/big-ip access policy manager","f5/big-ip advanced firewall manager","f5/big-ip advanced web application firewall","f5/big-ip analytics","f5/big-ip application acceleration manager","f5/big-ip application security manager","f5/big-ip ddos hybrid defender","f5/big-ip domain name system","f5/big-ip fraud protection service","f5/big-ip global traffic manager","f5/big-ip link controller","f5/big-ip local traffic manager","f5/big-ip policy enforcement manager","f5/ssl orchestrator"],"epss":{"score":0.62421,"percentile":0.99184,"date":"2026-10-30","history":[{"date":"2026-10-25","score":0.62421,"percentile":0.99179}]},"kev":{"listed":true,"dateAdded":"2022-01-18","dueDate":"2022-02-01","knownRansomwareCampaignUse":"Unknown","notes":"Apply updates per vendor instructions.\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-22991"},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"urgent","text":"Known to be exploited in the wild (CISA KEV, CISA remediation deadline 1 February 2022). Treat as an emergency change: patch or isolate now, then hunt for prior compromise."},"changes":[],"references":[{"url":"https://support.f5.com/csp/article/K56715231","tags":["Vendor Advisory"],"source":"f5sirt@f5.com"},{"url":"https://support.f5.com/csp/article/K56715231","tags":["Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-22991","tags":["US Government Resource"],"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-22991","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}