# CVE-2021-22991: F5 BIG-IP Traffic Management Microkernel Buffer Overflow

> CVE-2021-22991: F5 BIG-IP Traffic Management Microkernel Buffer Overflow. CVSS 9.8 (CVSS 3.1), in CISA KEV.

Canonical: https://rewindex.com/cve/CVE-2021-22991
Last updated: 2025-10-21T23:25:50Z

- Published: 2021-03-31 17:23 UTC · Updated: 2025-10-21 23:25 UTC · Assigner: f5
- CVSS: 9.8 (CVSS 3.1) · Severity: Critical · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS: 62.4%, 99th percentile (scored 2026-10-25)
- CISA KEV: yes, added 2022-01-18, federal due date 2022-02-01, ransomware use: Unknown

## 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.

## CISA required action

Apply updates per vendor instructions.

## Affected vendors and products

- n/a: BIG-IP

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2021-22991)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2021-22991)
- [https://support.f5.com/csp/article/K56715231](https://support.f5.com/csp/article/K56715231)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2021-22991 · Markdown: https://rewindex.com/cve/CVE-2021-22991.md · JSON: https://rewindex.com/api/v1/cves/CVE-2021-22991 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T03:12:58.665Z