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Fencer Vulns
high 7.5

CVE-2021-23009 json

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 Deni…

published 2021-05-10 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-10127

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 62%
public exploits
0
none known

Summary

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.

Patch / fix

  • f5 big-ip_access_policy_manager 15.1.3, 16.0.1.1
  • f5 big-ip_advanced_firewall_manager 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 big-ip_application_acceleration_manager 15.1.3, 16.0.1.1
  • f5 big-ip_application_security_manager 15.1.3, 16.0.1.1
  • f5 big-ip_ddos_hybrid_defender 15.1.3, 16.0.1.1
  • f5 big-ip_domain_name_system 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_local_traffic_manager 15.1.3, 16.0.1.1
  • f5 big-ip_policy_enforcement_manager 15.1.3, 16.0.1.1
  • f5 big-ip_ssl_orchestrator 15.1.3, 16.0.1.1

Exploit prediction

0.99% chance of exploitation in the next 30 days, higher than 62% 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

Classification

Weakness
  • CWE-835 Loop with Unreachable Exit Condition

References

Sources

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.