CVE-2020-5947

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-11-19 · updated 2026-06-17

Description

In versions 16.0.0-16.0.0.1 and 15.1.0-15.1.1, on specific BIG-IP platforms, attackers may be able to obtain TCP sequence numbers from the BIG-IP system that can be reused in future connections with the same source and destination port and IP numbers. Only these platforms are affected: BIG-IP 2000 series (C112), BIG-IP 4000 series (C113), BIG-IP i2000 series (C117), BIG-IP i4000 series (C115), BIG-IP Virtual Edition (VE).

Affected products

F5 BIG-IP APM: from 15.0.0 before 15.1.2; from 16.0.0 before 16.0.1 — fixed in 15.1.2, 16.0.1
BIG-IP: from 15.0.0 before 15.1.2; from 16.0.0 before 16.0.1 — fixed in 15.1.2, 16.0.1
F5 Big-Ip Advanced Web Application Firewall: from 15.0.0 before 15.1.2; from 16.0.0 before 16.0.1 — fixed in 15.1.2, 16.0.1
F5 Big-Ip Analytics: from 15.0.0 before 15.1.2; from 16.0.0 before 16.0.1 — fixed in 15.1.2, 16.0.1
F5 Networks, Inc. BIG-IP (AAM): from 15.0.0 before 15.1.2; from 16.0.0 before 16.0.1 — fixed in 15.1.2, 16.0.1
BIG-IP ASM: from 15.0.0 before 15.1.2; from 16.0.0 before 16.0.1 — fixed in 15.1.2, 16.0.1
F5 Big-Ip Ddos Hybrid Defender: from 15.0.0 before 15.1.2; from 16.0.0 before 16.0.1 — fixed in 15.1.2, 16.0.1
F5 BIG-IP DNS: from 15.0.0 before 15.1.2; from 16.0.0 before 16.0.1 — fixed in 15.1.2, 16.0.1
F5 Big-Ip Fraud Protection Service: from 15.0.0 before 15.1.2; from 16.0.0 before 16.0.1 — fixed in 15.1.2, 16.0.1
F5 Big-Ip Global Traffic Manager: from 15.0.0 through 15.1.2; from 16.0.0 before 16.0.1 — fixed in 16.0.1
F5 Big-Ip Link Controller: from 15.0.0 before 15.1.2; from 16.0.0 before 16.0.1 — fixed in 15.1.2, 16.0.1
F5 BIG-IP (LTM): from 15.0.0 before 15.1.2; from 16.0.0 before 16.0.1 — fixed in 15.1.2, 16.0.1
F5 Networks, Inc. BIG-IP (PEM): from 15.0.0 before 15.1.2; from 16.0.0 before 16.0.1 — fixed in 15.1.2, 16.0.1
F5 SSL Orchestrator: from 15.0.0 before 15.1.2; from 16.0.0 before 16.0.1 — fixed in 15.1.2, 16.0.1

How to fix

Upgrade to a fixed version: F5 BIG-IP APM 15.1.2, 16.0.1; BIG-IP 15.1.2, 16.0.1; F5 Big-Ip Advanced Web Application Firewall 15.1.2, 16.0.1; F5 Big-Ip Analytics 15.1.2, 16.0.1; F5 Networks, Inc. BIG-IP (AAM) 15.1.2, 16.0.1; BIG-IP ASM 15.1.2, 16.0.1; F5 Big-Ip Ddos Hybrid Defender 15.1.2, 16.0.1; F5 BIG-IP DNS 15.1.2, 16.0.1; F5 Big-Ip Fraud Protection Service 15.1.2, 16.0.1; F5 Big-Ip Global Traffic Manager 16.0.1; F5 Big-Ip Link Controller 15.1.2, 16.0.1; F5 BIG-IP (LTM) 15.1.2, 16.0.1. Check the vendor advisory for mitigations.

References

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