CISA KEV source record / CVE-2021-22991

F5 BIG-IP Traffic Management Microkernel Buffer Overflow

F5 / BIG-IP Traffic Management Microkernel

Known exploitation catalogNot a Secureline discoveryNot a live alert

The Traffic Management Microkernel of BIG-IP ASM Risk Engine has a buffer overflow vulnerability, leading to a bypassing of URL-based access controls.

CVE identifier: CVE-2021-22991
Added to KEV: Jan 18, 2022
CISA catalog dueDate: Feb 1, 2022

The dates above are catalog fields. The addition date does not establish when the vulnerability was discovered or first exploited. Confirm which requirements apply to your organisation separately.

Publisher's required action

Apply updates per vendor instructions.

This wording is attributed to the CISA snapshot. Verify current vendor guidance, affected versions and your deployment before applying changes.

Keep the signals separate.

Ransomware use, as reported by CISA: Unknown
CVSS severity: Not supplied by KEV
EPSS probability: Not available

No EPSS value was supplied for this record in the current snapshot. Unknown values are not treated as zero.

“Unknown” ransomware use is an unknown source field, not proof that ransomware activity has not occurred.

Source notes

https://nvd.nist.gov/vuln/detail/CVE-2021-22991

Source & freshness

Catalog version 2026.11.06
Source updated: Nov 6, 2026, 7:44 PM UTC
Successfully checked: Nov 8, 2026, 12:22 AM UTC

CISA source snapshot ↗CVE record ↗EPSS methodology ↗

Automated source record, not an editorial advisory or an independent discovery. No affected or fixed version is inferred, and no organisation-specific risk rating is generated.