CVE-2021-23009

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-835

Description

On BIG-IP version 16.0.x before 16.0.1.1 and 15.1.x before 15.1.3, malformed HTTP/2 requests may cause an infinite loop which causes a Denial of Service for Data Plane traffic. TMM takes the configured HA action when the TMM process is aborted. There is no control plane exposure, this is a data plane issue only. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Affected products

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

How to fix

Upgrade to a fixed version: F5 BIG-IP APM 15.1.3, 16.0.1.1; BIG-IP 15.1.3, 16.0.1.1; F5 Big-Ip Advanced Web Application Firewall 15.1.3, 16.0.1.1; F5 Big-Ip Analytics 15.1.3, 16.0.1.1; F5 Networks, Inc. BIG-IP (AAM) 15.1.3, 16.0.1.1; BIG-IP ASM 15.1.3, 16.0.1.1; F5 Big-Ip Ddos Hybrid Defender 15.1.3, 16.0.1.1; F5 BIG-IP DNS 15.1.3, 16.0.1.1; F5 Big-Ip Fraud Protection Service 15.1.3, 16.0.1.1; F5 Big-Ip Global Traffic Manager 15.1.3, 16.0.1.1; F5 Big-Ip Link Controller 15.1.3, 16.0.1.1; F5 BIG-IP (LTM) 15.1.3, 16.0.1.1. Check the vendor advisory for mitigations.

References

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