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

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: yes — in CISA KEV since 2022-01-18
EPSS: 62.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-03-31 · updated 2026-06-17
Weakness: CWE-119

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.

Affected products

F5 BIG-IP APM: from 12.1.0 before 12.1.5.3; from 13.1.0 before 13.1.3.6; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.2.1; from 16.0.0 before 16.0.1.1 — fixed in 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
BIG-IP: from 12.1.0 before 12.1.5.3; from 13.1.0 before 13.1.3.6; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.2.1; from 16.0.0 before 16.0.1.1 — fixed in 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
F5 Big-Ip Advanced Web Application Firewall: from 12.1.0 before 12.1.5.3; from 13.1.0 before 13.1.3.6; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.2.1; from 16.0.0 before 16.0.1.1 — fixed in 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
F5 Big-Ip Analytics: from 12.1.0 before 12.1.5.3; from 13.1.0 before 13.1.3.6; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.2.1; from 16.0.0 before 16.0.1.1 — fixed in 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
F5 Networks, Inc. BIG-IP (AAM): from 12.1.0 before 12.1.5.3; from 13.1.0 before 13.1.3.6; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.2.1; from 16.0.0 before 16.0.1.1 — fixed in 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
BIG-IP ASM: from 12.1.0 before 12.1.5.3; from 13.1.0 before 13.1.3.6; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.2.1; from 16.0.0 before 16.0.1.1 — fixed in 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
F5 Big-Ip Ddos Hybrid Defender: from 12.1.0 before 12.1.5.3; from 13.1.0 before 13.1.3.6; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.2.1; from 16.0.0 before 16.0.1.1 — fixed in 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
F5 BIG-IP DNS: from 12.1.0 before 12.1.5.3; from 13.1.0 before 13.1.3.6; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.2.1; from 16.0.0 before 16.0.1.1 — fixed in 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
F5 Big-Ip Fraud Protection Service: from 12.1.0 before 12.1.5.3; from 13.1.0 before 13.1.3.6; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.2.1; from 16.0.0 before 16.0.1.1 — fixed in 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
F5 Big-Ip Global Traffic Manager: from 12.1.0 before 12.1.5.3; from 13.1.0 before 13.1.3.6; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.2.1; from 16.0.0 before 16.0.1.1 — fixed in 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
F5 Big-Ip Link Controller: from 12.1.0 before 12.1.5.3; from 13.1.0 before 13.1.3.6; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.2.1; from 16.0.0 before 16.0.1.1 — fixed in 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
F5 BIG-IP (LTM): from 12.1.0 before 12.1.5.3; from 13.1.0 before 13.1.3.6; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.2.1; from 16.0.0 before 16.0.1.1 — fixed in 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
F5 Networks, Inc. BIG-IP (PEM): from 12.1.0 before 12.1.5.3; from 13.1.0 before 13.1.3.6; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.2.1; from 16.0.0 before 16.0.1.1 — fixed in 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
F5 SSL Orchestrator: from 12.1.0 before 12.1.5.3; from 13.1.0 before 13.1.3.6; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.2.1; from 16.0.0 before 16.0.1.1 — fixed in 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1

How to fix

Upgrade to a fixed version: F5 BIG-IP APM 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1; BIG-IP 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1; F5 Big-Ip Advanced Web Application Firewall 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1; F5 Big-Ip Analytics 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1; F5 Networks, Inc. BIG-IP (AAM) 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1; BIG-IP ASM 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1; F5 Big-Ip Ddos Hybrid Defender 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1; F5 BIG-IP DNS 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1; F5 Big-Ip Fraud Protection Service 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1; F5 Big-Ip Global Traffic Manager 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1; F5 Big-Ip Link Controller 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1; F5 BIG-IP (LTM) 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1. Check the vendor advisory for mitigations.

References

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