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.

Published: 2021-03-31 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-23000 is rated Moderate Risk (49.9/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.93%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-23000

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.65% 0.93% +0.29%
2 2025-03-30 0.77% 0.65% -0.12%
3 2025-03-29 — 0.77% —

Full EPSS history (9 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-23000

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2021-23000

Affected software / configurations for CVE-2021-23000

Vendor Product Version Raw CPE
f5 big-ip_access_policy_manager >= 13.1.3.4, < 13.1.3.6 cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*
f5 big-ip_access_policy_manager 12.1.5.2 cpe:2.3:a:f5:big-ip_access_policy_manager:12.1.5.2:*:*:*:*:*:*:*
f5 big-ip_advanced_firewall_manager >= 13.1.3.4, < 13.1.3.6 cpe:2.3:a:f5:big-ip_advanced_firewall_manager:*:*:*:*:*:*:*:*
f5 big-ip_advanced_firewall_manager 12.1.5.2 cpe:2.3:a:f5:big-ip_advanced_firewall_manager:12.1.5.2:*:*:*:*:*:*:*
f5 big-ip_advanced_web_application_firewall >= 13.1.3.4, < 13.1.3.6 cpe:2.3:a:f5:big-ip_advanced_web_application_firewall:*:*:*:*:*:*:*:*
f5 big-ip_advanced_web_application_firewall 12.1.5.2 cpe:2.3:a:f5:big-ip_advanced_web_application_firewall:12.1.5.2:*:*:*:*:*:*:*
f5 big-ip_analytics >= 13.1.3.4, < 13.1.3.6 cpe:2.3:a:f5:big-ip_analytics:*:*:*:*:*:*:*:*
f5 big-ip_analytics 12.1.5.2 cpe:2.3:a:f5:big-ip_analytics:12.1.5.2:*:*:*:*:*:*:*
f5 big-ip_application_acceleration_manager >= 13.1.3.4, < 13.1.3.6 cpe:2.3:a:f5:big-ip_application_acceleration_manager:*:*:*:*:*:*:*:*
f5 big-ip_application_acceleration_manager 12.1.5.2 cpe:2.3:a:f5:big-ip_application_acceleration_manager:12.1.5.2:*:*:*:*:*:*:*
f5 big-ip_application_security_manager >= 13.1.3.4, < 13.1.3.6 cpe:2.3:a:f5:big-ip_application_security_manager:*:*:*:*:*:*:*:*
f5 big-ip_application_security_manager 12.1.5.2 cpe:2.3:a:f5:big-ip_application_security_manager:12.1.5.2:*:*:*:*:*:*:*
f5 big-ip_ddos_hybrid_defender >= 13.1.3.4, < 13.1.3.6 cpe:2.3:a:f5:big-ip_ddos_hybrid_defender:*:*:*:*:*:*:*:*
f5 big-ip_ddos_hybrid_defender 12.1.5.2 cpe:2.3:a:f5:big-ip_ddos_hybrid_defender:12.1.5.2:*:*:*:*:*:*:*
f5 big-ip_domain_name_system >= 13.1.3.4, < 13.1.3.6 cpe:2.3:a:f5:big-ip_domain_name_system:*:*:*:*:*:*:*:*
f5 big-ip_domain_name_system 12.1.5.2 cpe:2.3:a:f5:big-ip_domain_name_system:12.1.5.2:*:*:*:*:*:*:*
f5 big-ip_fraud_protection_service >= 13.1.3.4, < 13.1.3.6 cpe:2.3:a:f5:big-ip_fraud_protection_service:*:*:*:*:*:*:*:*
f5 big-ip_fraud_protection_service 12.1.5.2 cpe:2.3:a:f5:big-ip_fraud_protection_service:12.1.5.2:*:*:*:*:*:*:*
f5 big-ip_global_traffic_manager >= 13.1.3.4, < 13.1.3.6 cpe:2.3:a:f5:big-ip_global_traffic_manager:*:*:*:*:*:*:*:*
f5 big-ip_global_traffic_manager 12.1.5.2 cpe:2.3:a:f5:big-ip_global_traffic_manager:12.1.5.2:*:*:*:*:*:*:*
f5 big-ip_link_controller >= 13.1.3.4, < 13.1.3.6 cpe:2.3:a:f5:big-ip_link_controller:*:*:*:*:*:*:*:*
f5 big-ip_link_controller 12.1.5.2 cpe:2.3:a:f5:big-ip_link_controller:12.1.5.2:*:*:*:*:*:*:*
f5 big-ip_local_traffic_manager >= 13.1.3.4, < 13.1.3.6 cpe:2.3:a:f5:big-ip_local_traffic_manager:*:*:*:*:*:*:*:*
f5 big-ip_local_traffic_manager 12.1.5.2 cpe:2.3:a:f5:big-ip_local_traffic_manager:12.1.5.2:*:*:*:*:*:*:*
f5 big-ip_policy_enforcement_manager >= 13.1.3.4, < 13.1.3.6 cpe:2.3:a:f5:big-ip_policy_enforcement_manager:*:*:*:*:*:*:*:*
f5 big-ip_policy_enforcement_manager 12.1.5.2 cpe:2.3:a:f5:big-ip_policy_enforcement_manager:12.1.5.2:*:*:*:*:*:*:*
f5 ssl_orchestrator >= 13.1.3.4, < 13.1.3.6 cpe:2.3:a:f5:ssl_orchestrator:*:*:*:*:*:*:*:*
f5 ssl_orchestrator 12.1.5.2 cpe:2.3:a:f5:ssl_orchestrator:12.1.5.2:*:*:*:*:*:*:*

References for CVE-2021-23000

cvelogic Threat Intelligence