CVE-2021-22991
F5 BIG-IP Traffic Management Microkernel Buffer Overflow
- Critical 9.8
- Exploited: added to CISA KEV 18 Jan 2022
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.
Key facts
- Published
- 31 Mar 2021
- Last changed
- 21 Oct 2025
- Assigned by
- f5
- KEV added
- 18 Jan 2022
- KEV fix due
- 1 Feb 2022
- EPSS
- 62.421% likely to be exploited in the next 30 days, higher than 99.2% of CVEs (scores for 15 Nov 2026)
- SSVC (CISA)
- Exploitation: active; Automatable: yes; Technical impact: total
Severity scores
Each score is shown as its source gave it. They are not averaged or merged.
- 9.8CVSS 3.1, Criticalfrom CISA (ADP container)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
What to do
- Apply updates per vendor instructions.CISA KEV required action
Historical context and remediation
This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.
No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.
Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.
Affected products
| Vendor | Product | Versions |
|---|---|---|
| n/a | BIG-IP |
|
Timeline
- 31 Mar 2021 Published
- 18 Jan 2022 CVE-2021-22991 added to CISA KEV
- 18 Jan 2022 Added to the CISA KEV catalogue