CVE-2021-23011

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-05-10 · updated 2026-06-17
Weakness: CWE-400

Description

On versions 16.0.x before 16.0.1.1, 15.1.x before 15.1.3, 14.1.x before 14.1.4, 13.1.x before 13.1.4, 12.1.x before 12.1.6, and 11.6.x before 11.6.5.3, when the BIG-IP system is buffering packet fragments for reassembly, the Traffic Management Microkernel (TMM) may consume an excessive amount of resources, eventually leading to a restart and failover event. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Affected products

F5 BIG-IP APM: from 11.6.1 before 11.6.5.3; from 12.1.0 before 12.1.6; from 13.1.0 before 13.1.4; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.3; from 16.0.0 before 16.0.1.1 — fixed in 11.6.5.3, 12.1.6, 13.1.4, 14.1.4, 15.1.3, 16.0.1.1
BIG-IP: from 11.6.1 before 11.6.5.3; from 12.1.0 before 12.1.6; from 13.1.0 before 13.1.4; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.3; from 16.0.0 before 16.0.1.1 — fixed in 11.6.5.3, 12.1.6, 13.1.4, 14.1.4, 15.1.3, 16.0.1.1
F5 Big-Ip Advanced Web Application Firewall: from 11.6.1 before 11.6.5.3; from 12.1.0 before 12.1.6; from 13.1.0 before 13.1.4; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.3; from 16.0.0 before 16.0.1.1 — fixed in 11.6.5.3, 12.1.6, 13.1.4, 14.1.4, 15.1.3, 16.0.1.1
F5 Big-Ip Analytics: from 11.6.1 before 11.6.5.3; from 12.1.0 before 12.1.6; from 13.1.0 before 13.1.4; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.3; from 16.0.0 before 16.0.1.1 — fixed in 11.6.5.3, 12.1.6, 13.1.4, 14.1.4, 15.1.3, 16.0.1.1
F5 Networks, Inc. BIG-IP (AAM): from 11.6.1 before 11.6.5.3; from 12.1.0 before 12.1.6; from 13.1.0 before 13.1.4; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.3; from 16.0.0 before 16.0.1.1 — fixed in 11.6.5.3, 12.1.6, 13.1.4, 14.1.4, 15.1.3, 16.0.1.1
BIG-IP ASM: from 11.6.1 before 11.6.5.3; from 12.1.0 before 12.1.6; from 13.1.0 before 13.1.4; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.3; from 16.0.0 before 16.0.1.1 — fixed in 11.6.5.3, 12.1.6, 13.1.4, 14.1.4, 15.1.3, 16.0.1.1
F5 Big-Ip Ddos Hybrid Defender: from 11.6.1 before 11.6.5.3; from 12.1.0 before 12.1.6; from 13.1.0 before 13.1.4; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.3; from 16.0.0 before 16.0.1.1 — fixed in 11.6.5.3, 12.1.6, 13.1.4, 14.1.4, 15.1.3, 16.0.1.1
F5 BIG-IP DNS: from 11.6.1 before 11.6.5.3; from 12.1.0 before 12.1.6; from 13.1.0 before 13.1.4; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.3; from 16.0.0 before 16.0.1.1 — fixed in 11.6.5.3, 12.1.6, 13.1.4, 14.1.4, 15.1.3, 16.0.1.1
F5 Big-Ip Fraud Protection Service: from 11.6.1 before 11.6.5.3; from 12.1.0 before 12.1.6; from 13.1.0 before 13.1.4; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.3; from 16.0.0 before 16.0.1.1 — fixed in 11.6.5.3, 12.1.6, 13.1.4, 14.1.4, 15.1.3, 16.0.1.1
F5 Big-Ip Global Traffic Manager: from 11.6.1 before 11.6.5.3; from 12.1.0 before 12.1.6; from 13.1.0 before 13.1.4; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.3; from 16.0.0 before 16.0.1.1 — fixed in 11.6.5.3, 12.1.6, 13.1.4, 14.1.4, 15.1.3, 16.0.1.1
F5 Big-Ip Link Controller: from 11.6.1 before 11.6.5.3; from 12.1.0 before 12.1.6; from 13.1.0 before 13.1.4; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.3; from 16.0.0 before 16.0.1.1 — fixed in 11.6.5.3, 12.1.6, 13.1.4, 14.1.4, 15.1.3, 16.0.1.1
F5 BIG-IP (LTM): from 11.6.1 before 11.6.5.3; from 12.1.0 before 12.1.6; from 13.1.0 before 13.1.4; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.3; from 16.0.0 before 16.0.1.1 — fixed in 11.6.5.3, 12.1.6, 13.1.4, 14.1.4, 15.1.3, 16.0.1.1
F5 Networks, Inc. BIG-IP (PEM): from 11.6.1 before 11.6.5.3; from 12.1.0 before 12.1.6; from 13.1.0 before 13.1.4; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.3; from 16.0.0 before 16.0.1.1 — fixed in 11.6.5.3, 12.1.6, 13.1.4, 14.1.4, 15.1.3, 16.0.1.1
F5 Big-Ip Ssl Orchestrator: from 11.6.1 before 11.6.5.3; from 12.1.0 before 12.1.6; from 13.1.0 before 13.1.4; from 14.1.0 before 14.1.4; from 15.1.0 before 15.1.3; from 16.0.0 before 16.0.1.1 — fixed in 11.6.5.3, 12.1.6, 13.1.4, 14.1.4, 15.1.3, 16.0.1.1

How to fix

Upgrade to a fixed version: F5 BIG-IP APM 11.6.5.3, 12.1.6, 13.1.4, 14.1.4; BIG-IP 11.6.5.3, 12.1.6, 13.1.4, 14.1.4; F5 Big-Ip Advanced Web Application Firewall 11.6.5.3, 12.1.6, 13.1.4, 14.1.4; F5 Big-Ip Analytics 11.6.5.3, 12.1.6, 13.1.4, 14.1.4; F5 Networks, Inc. BIG-IP (AAM) 11.6.5.3, 12.1.6, 13.1.4, 14.1.4; BIG-IP ASM 11.6.5.3, 12.1.6, 13.1.4, 14.1.4; F5 Big-Ip Ddos Hybrid Defender 11.6.5.3, 12.1.6, 13.1.4, 14.1.4; F5 BIG-IP DNS 11.6.5.3, 12.1.6, 13.1.4, 14.1.4; F5 Big-Ip Fraud Protection Service 11.6.5.3, 12.1.6, 13.1.4, 14.1.4; F5 Big-Ip Global Traffic Manager 11.6.5.3, 12.1.6, 13.1.4, 14.1.4; F5 Big-Ip Link Controller 11.6.5.3, 12.1.6, 13.1.4, 14.1.4; F5 BIG-IP (LTM) 11.6.5.3, 12.1.6, 13.1.4, 14.1.4. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2021-23011 or the next vulnerability affects your stack