How severe is CVE-2021-23000?

CVE-2021-23000 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-2021-23000 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (56th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-23000?

CVE-2021-23000 primarily affects F5 Big-ip Access Policy Manager. In total, 28 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-23000?

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-2021-23000 published?

CVE-2021-23000 was published on 2021-03-31 and last updated on 2026-06-17.

CVE-2021-23000

CVE-2021-23000 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.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 4.3
EPSS exploit prediction: 1% (56th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: F5 Big-ip Access Policy Manager
Published: 2021-03-31
Last modified: 2026-06-17

Description

On BIG-IP versions 13.1.3.4-13.1.3.6 and 12.1.5.2, if the tmm.http.rfc.enforcement BigDB key is enabled in a BIG-IP system, or the Bad host header value is checked in the AFM HTTP security profile associated with a virtual server, in rare instances, a specific sequence of malicious requests may cause TMM to restart. Note: Software versions which have reached End of Software Development (EoSD) are not evaluated.

Frequently asked questions

What is CVE-2021-23000?: On BIG-IP versions 13.1.3.4-13.1.3.6 and 12.1.5.2, if the tmm.http.rfc.enforcement BigDB key is enabled in a BIG-IP system, or the Bad host header value is checked in the AFM HTTP security profile associated with a virtual server, in rare instances, a specific sequence of malicious requests may cause TMM to restart. Note: Software versions which have reached End of Software Development (EoSD) are not evaluated.
How severe is CVE-2021-23000?: CVE-2021-23000 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-2021-23000 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (56th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-23000?: CVE-2021-23000 primarily affects F5 Big-ip Access Policy Manager. In total, 28 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-23000?: 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-2021-23000 published?: CVE-2021-23000 was published on 2021-03-31 and last updated on 2026-06-17.

References

https://support.f5.com/csp/article/K34441555

Affected products (28)

cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_access_policy_manager:12.1.5.2:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_advanced_firewall_manager:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_advanced_firewall_manager:12.1.5.2:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_advanced_web_application_firewall:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_advanced_web_application_firewall:12.1.5.2:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_analytics:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_analytics:12.1.5.2:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_application_acceleration_manager:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_application_acceleration_manager:12.1.5.2:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_application_security_manager:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_application_security_manager:12.1.5.2:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_ddos_hybrid_defender:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_ddos_hybrid_defender:12.1.5.2:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_domain_name_system:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_domain_name_system:12.1.5.2:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_fraud_protection_service:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_fraud_protection_service:12.1.5.2:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_global_traffic_manager:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_global_traffic_manager:12.1.5.2:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_link_controller:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_link_controller:12.1.5.2:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_local_traffic_manager:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_local_traffic_manager:12.1.5.2:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_policy_enforcement_manager:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:big-ip_policy_enforcement_manager:12.1.5.2:*:*:*:*:*:*:*
cpe:2.3:a:f5:ssl_orchestrator:*:*:*:*:*:*:*:*
cpe:2.3:a:f5:ssl_orchestrator:12.1.5.2:*:*:*:*:*:*:*

More vulnerabilities in F5 Big-ip Access Policy Manager

CVE-2023-41373 — Critical (CVSS 9.9): A directory traversal vulnerability exists in the BIG-IP Configuration Utility that may allow an authenticated attacker…
CVE-2021-22987 — Critical (CVSS 9.9): 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…
CVE-2025-53521 — Critical (CVSS 9.8): When a BIG-IP APM access policy is configured on a virtual server, specific malicious traffic can lead to Remote Code…
CVE-2023-46747 — Critical (CVSS 9.8): Undisclosed requests may bypass configuration utility authentication, allowing an attacker with network access to the…
CVE-2022-1388 — Critical (CVSS 9.8): On F5 BIG-IP 16.1.x versions prior to 16.1.2.2, 15.1.x versions prior to 15.1.5.1, 14.1.x versions prior to 14.1.4.6,…
CVE-2021-23008 — Critical (CVSS 9.8): On version 15.1.x before 15.1.3, 14.1.x before 14.1.4, 13.1.x before 13.1.4, 12.1.x before 12.1.6, and all versions of…

All CVEs affecting F5 Big-ip Access Policy Manager →