How severe is CVE-2021-23009?

CVE-2021-23009 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-23009 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-23009?

CVE-2021-23009 primarily affects F5 Big-ip Access Policy Manager. In total, 14 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-23009?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-23009 published?

CVE-2021-23009 was published on 2021-05-10 and last updated on 2026-06-17.

CVE-2021-23009

CVE-2021-23009 is a high-severity vulnerability in F5 Big-ip Access Policy Manager with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-835.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 1% (58th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-835
Affected product: F5 Big-ip Access Policy Manager
Published: 2021-05-10
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-23009?: 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.
How severe is CVE-2021-23009?: CVE-2021-23009 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-23009 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-23009?: CVE-2021-23009 primarily affects F5 Big-ip Access Policy Manager. In total, 14 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-23009?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-23009 published?: CVE-2021-23009 was published on 2021-05-10 and last updated on 2026-06-17.

References

https://support.f5.com/csp/article/K90603426

Affected products (14)

cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_advanced_firewall_manager:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_advanced_web_application_firewall:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_analytics:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_application_acceleration_manager:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_application_security_manager:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_ddos_hybrid_defender:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_domain_name_system:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_fraud_protection_service:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_global_traffic_manager:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_link_controller:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_local_traffic_manager:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_policy_enforcement_manager:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_ssl_orchestrator:*:*:*:*:*:*:*:*

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