in BIG-IP versions 15.1.0-15.1.0.4, 15.0.0-15.0.1.3, 14.1.0-14.1.2.6, 13.1.0-13.1.3.4, 12.1.0-12.1.5.1, and 11.6.1-11.6.5.2, Syn flood caus…

published 2020-08-26 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-27075

cvss: 7.5; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 1.0%; EPSS 1.0% chance of exploitation in 30 days, percentile 64%
public exploits: 0; none known

in BIG-IP versions 15.1.0-15.1.0.4, 15.0.0-15.0.1.3, 14.1.0-14.1.2.6, 13.1.0-13.1.3.4, 12.1.0-12.1.5.1, and 11.6.1-11.6.5.2, Syn flood causes large number of MCPD context messages destined to secondary blades consuming memory leading to MCPD failure. This issue affects only VIPRION hosts with two or more blades installed. Single-blade VIPRION hosts are not affected.

Patch / fix

fixed in 11

f5 big-ip_access_policy_manager 12.1.5.2, 14.1.2.7, 15.0.1.4, 15.1.0.5
f5 big-ip_advanced_firewall_manager 12.1.5.2, 14.1.2.7, 15.0.1.4, 15.1.0.5
f5 big-ip_analytics 12.1.5.2, 14.1.2.7, 15.0.1.4, 15.1.0.5
f5 big-ip_application_acceleration_manager 12.1.5.2, 14.1.2.7, 15.0.1.4, 15.1.0.5
f5 big-ip_application_security_manager 12.1.5.2, 14.1.2.7, 15.0.1.4, 15.1.0.5
f5 big-ip_domain_name_system 12.1.5.2, 14.1.2.7, 15.0.1.4, 15.1.0.5
f5 big-ip_fraud_protection_service 12.1.5.2, 14.1.2.7, 15.0.1.4, 15.1.0.5
f5 big-ip_global_traffic_manager 12.1.5.2, 14.1.2.7, 15.0.1.4, 15.1.0.5
f5 big-ip_link_controller 12.1.5.2, 14.1.2.7, 15.0.1.4, 15.1.0.5
f5 big-ip_local_traffic_manager 12.1.5.2, 14.1.2.7, 15.0.1.4, 15.1.0.5
f5 big-ip_policy_enforcement_manager 12.1.5.2, 14.1.2.7, 15.0.1.4, 15.1.0.5

Exploit prediction

1.04% chance of exploitation in the next 30 days, higher than 64% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
NVD	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:N/A:P

Affected products

n/a BIG-IP

References

support.f5.com /csp/article/K00103216
vendor-advisory

Sources

CVE List CVE-2020-5921
NVD CVE-2020-5921

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary