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CVE-2021-22991

90
FAUCET Score

CVE-2021-22991 is a critical buffer overflow vulnerability affecting F5 BIG-IP versions 16.0.x, 15.1.x, 14.1.x, 13.1.x, and 12.1.x. Undisclosed requests to a virtual server can be mishandled by the Traffic Management Microkernel (TMM) URI normalization, leading to a Denial of Service (DoS) attack. In certain scenarios, this vulnerability could also enable URL-based access control bypass or remote code execution (RCE). With a CVSS score of 9.8 (CRITICAL), it is easily exploitable over the network without authentication and has a high impact on confidentiality, integrity, and availability. This vulnerability is actively exploited in the wild, as confirmed by its inclusion in CISA's KEV catalog, and has garnered significant community discussion and media coverage, despite the lack of public exploit code on platforms like Metasploit or ExploitDB.

Impacted Technologies

VendorProductVersion(s)CPE
>= 12.1.0, < 12.1.5.3CPE matchmatch criteria
cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*
>= 13.1.0, < 13.1.3.6CPE matchmatch criteria
cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*
>= 14.1.0, < 14.1.4CPE matchmatch criteria
cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*
>= 15.1.0, < 15.1.2.1CPE matchmatch criteria
cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*
>= 16.0.0, < 16.0.1.1CPE matchmatch criteria
cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
61.06%
Probability of exploitation in next 30 days
EPSS Percentile
99.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Added to KEV · Jan 18, 2022
This CVE's current EPSS score of 0.6106 is in the 97th percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

cisa.gov / known-exploited-vulnerabilities-catalog
US Government Resource
support.f5.com / csp/article/K56715231
Vendor Advisory