What is CVE-2021-22991?

CVE-2021-22991 is a critical-severity vulnerability in F5 Big-Ip Access Policy Manager, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.8/10. Published 2021-03-31.

How severe is CVE-2021-22991?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2021-22991 known to be exploited?

Yes. CVE-2021-22991 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-01-18), indicating it is being actively exploited. 8 public proof-of-concept repositories are indexed.

Buffer overflow in F5 Big-Ip Access Policy Manager

CVE-2021-22991

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.

Vulnerability class: Buffer Overflow

EPSS: 0.611 (99.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

Weakness classification (CWE)

CWE-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2022-01-18. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2022-02-01.

Required action: Apply updates per vendor instructions.

Public proof-of-concept exploits

References

f5sirt@f5.com (x_refsource_MISC, Vendor Advisory)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)

Frequently asked questions

What is CVE-2021-22991?: CVE-2021-22991 is a critical-severity vulnerability in F5 Big-Ip Access Policy Manager, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.8/10. Published 2021-03-31.
How severe is CVE-2021-22991?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2021-22991 known to be exploited?: Yes. CVE-2021-22991 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-01-18), indicating it is being actively exploited. 8 public proof-of-concept repositories are indexed.