CVE-2021-22998

Severity: medium (CVSS 5.3 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: 2021-03-31 · updated 2026-06-17

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, 12.1.x before 12.1.5.3, and 11.6.x before 11.6.5.3, SYN flood protection thresholds are not enforced in secure network address translation (SNAT) listeners. Note: Software versions which have reached End of Software Development (EoSD) are not evaluated.

Affected products

F5 BIG-IP APM: from 11.6.1 before 11.6.5.3; from 12.1.0 before 12.1.5.3; 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 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
BIG-IP: from 11.6.1 before 11.6.5.3; 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 11.6.5.3, 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 11.6.1 before 11.6.5.3; 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 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
F5 Big-Ip Analytics: from 11.6.1 before 11.6.5.3; 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 11.6.5.3, 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 11.6.1 before 11.6.5.3; 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 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
BIG-IP ASM: from 11.6.1 before 11.6.5.3; 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 11.6.5.3, 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 11.6.1 before 11.6.5.3; 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 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
F5 BIG-IP DNS: from 11.6.1 before 11.6.5.3; 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 11.6.5.3, 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 11.6.1 before 11.6.5.3; 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 11.6.5.3, 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 11.6.1 before 11.6.5.3; 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 11.6.5.3, 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 11.6.1 before 11.6.5.3; 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 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
F5 BIG-IP (LTM): from 11.6.1 before 11.6.5.3; 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 11.6.5.3, 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 11.6.1 before 11.6.5.3; 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 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4, 15.1.2.1, 16.0.1.1
F5 SSL Orchestrator: from 11.6.1 before 11.6.5.3; 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 11.6.5.3, 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 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4; BIG-IP 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4; F5 Big-Ip Advanced Web Application Firewall 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4; F5 Big-Ip Analytics 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4; F5 Networks, Inc. BIG-IP (AAM) 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4; BIG-IP ASM 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4; F5 Big-Ip Ddos Hybrid Defender 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4; F5 BIG-IP DNS 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4; F5 Big-Ip Fraud Protection Service 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4; F5 Big-Ip Global Traffic Manager 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4; F5 Big-Ip Link Controller 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4; F5 BIG-IP (LTM) 11.6.5.3, 12.1.5.3, 13.1.3.6, 14.1.4. Check the vendor advisory for mitigations.

References

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