CVE-2021-22991

Exp

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, and 12.1.x before 12.1.5.3, undisclosed requests to a virtual server may be incorrectly handled by the Traffic Management Microkernel (TMM) URI normalization, which may trigger a buffer overflow, resulting in a DoS attack. In certain situations, it may theoretically allow bypass of URL based access control or remote code execution (RCE). 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：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-22991 is rated Critical Active Threat (93.9/100): CVSS Critical severity, with high exploitation likelihood (EPSS 61.06%, 99th percentile). CISA KEV confirms active exploitation (added 2022-01-18) affecting F5 / BIG-IP Traffic Management Microkernel. a weakness (CWE-119) Unauthenticated remote administrative access may be possible. The CISA remediation deadline has passed—treat as an emergency patch priority.

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

CISA KEV Record for CVE-2021-22991

Name: F5 BIG-IP Traffic Management Microkernel Buffer Overflow · CISA KEV detail

Exploit added: 2022-01-18

Action due: 2022-02-01

Required action: Apply updates per vendor instructions.

Exploit prediction scoring system (EPSS) score for CVE-2021-22991

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 73.09% 61.06% -12.03%
2 2026-02-12 66.26% 73.09% +6.84%
3 2025-11-21 — 66.26% —

Full EPSS history (36 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-22991

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 134c704f-9b21-4f2e-91b3-4a467353bcc0
6.8 2.0 MEDIUM
AV:N/AC:M/Au:N/C:P/I:P/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:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.6 6.4 [email protected]

Weakness enumeration for CVE-2021-22991

Affected software / configurations for CVE-2021-22991

Vendor Product Version Raw CPE
f5 big-ip_access_policy_manager >= 12.1.0, < 12.1.5.3 cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*
f5 big-ip_access_policy_manager >= 13.1.0, < 13.1.3.6 cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*
f5 big-ip_access_policy_manager >= 14.1.0, < 14.1.4 cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*
f5 big-ip_access_policy_manager >= 15.1.0, < 15.1.2.1 cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*
f5 big-ip_access_policy_manager >= 16.0.0, < 16.0.1.1 cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*
f5 big-ip_advanced_firewall_manager >= 12.1.0, < 12.1.5.3 cpe:2.3:a:f5:big-ip_advanced_firewall_manager:*:*:*:*:*:*:*:*
f5 big-ip_advanced_firewall_manager >= 13.1.0, < 13.1.3.6 cpe:2.3:a:f5:big-ip_advanced_firewall_manager:*:*:*:*:*:*:*:*
f5 big-ip_advanced_firewall_manager >= 14.1.0, < 14.1.4 cpe:2.3:a:f5:big-ip_advanced_firewall_manager:*:*:*:*:*:*:*:*
f5 big-ip_advanced_firewall_manager >= 15.1.0, < 15.1.2.1 cpe:2.3:a:f5:big-ip_advanced_firewall_manager:*:*:*:*:*:*:*:*
f5 big-ip_advanced_firewall_manager >= 16.0.0, < 16.0.1.1 cpe:2.3:a:f5:big-ip_advanced_firewall_manager:*:*:*:*:*:*:*:*
f5 big-ip_advanced_web_application_firewall >= 12.1.0, < 12.1.5.3 cpe:2.3:a:f5:big-ip_advanced_web_application_firewall:*:*:*:*:*:*:*:*
f5 big-ip_advanced_web_application_firewall >= 13.1.0, < 13.1.3.6 cpe:2.3:a:f5:big-ip_advanced_web_application_firewall:*:*:*:*:*:*:*:*
f5 big-ip_advanced_web_application_firewall >= 14.1.0, < 14.1.4 cpe:2.3:a:f5:big-ip_advanced_web_application_firewall:*:*:*:*:*:*:*:*
f5 big-ip_advanced_web_application_firewall >= 15.1.0, < 15.1.2.1 cpe:2.3:a:f5:big-ip_advanced_web_application_firewall:*:*:*:*:*:*:*:*
f5 big-ip_advanced_web_application_firewall >= 16.0.0, < 16.0.1.1 cpe:2.3:a:f5:big-ip_advanced_web_application_firewall:*:*:*:*:*:*:*:*
f5 big-ip_analytics >= 12.1.0, < 12.1.5.3 cpe:2.3:a:f5:big-ip_analytics:*:*:*:*:*:*:*:*
f5 big-ip_analytics >= 13.1.0, < 13.1.3.6 cpe:2.3:a:f5:big-ip_analytics:*:*:*:*:*:*:*:*
f5 big-ip_analytics >= 14.1.0, < 14.1.4 cpe:2.3:a:f5:big-ip_analytics:*:*:*:*:*:*:*:*
f5 big-ip_analytics >= 15.1.0, < 15.1.2.1 cpe:2.3:a:f5:big-ip_analytics:*:*:*:*:*:*:*:*
f5 big-ip_analytics >= 16.0.0, < 16.0.1.1 cpe:2.3:a:f5:big-ip_analytics:*:*:*:*:*:*:*:*
f5 big-ip_application_acceleration_manager >= 12.1.0, < 12.1.5.3 cpe:2.3:a:f5:big-ip_application_acceleration_manager:*:*:*:*:*:*:*:*
f5 big-ip_application_acceleration_manager >= 13.1.0, < 13.1.3.6 cpe:2.3:a:f5:big-ip_application_acceleration_manager:*:*:*:*:*:*:*:*
f5 big-ip_application_acceleration_manager >= 14.1.0, < 14.1.4 cpe:2.3:a:f5:big-ip_application_acceleration_manager:*:*:*:*:*:*:*:*
f5 big-ip_application_acceleration_manager >= 15.1.0, < 15.1.2.1 cpe:2.3:a:f5:big-ip_application_acceleration_manager:*:*:*:*:*:*:*:*
f5 big-ip_application_acceleration_manager >= 16.0.0, < 16.0.1.1 cpe:2.3:a:f5:big-ip_application_acceleration_manager:*:*:*:*:*:*:*:*
f5 big-ip_application_security_manager >= 12.1.0, < 12.1.5.3 cpe:2.3:a:f5:big-ip_application_security_manager:*:*:*:*:*:*:*:*
f5 big-ip_application_security_manager >= 13.1.0, < 13.1.3.6 cpe:2.3:a:f5:big-ip_application_security_manager:*:*:*:*:*:*:*:*
f5 big-ip_application_security_manager >= 14.1.0, < 14.1.4 cpe:2.3:a:f5:big-ip_application_security_manager:*:*:*:*:*:*:*:*
f5 big-ip_application_security_manager >= 15.1.0, < 15.1.2.1 cpe:2.3:a:f5:big-ip_application_security_manager:*:*:*:*:*:*:*:*
f5 big-ip_application_security_manager >= 16.0.0, < 16.0.1.1 cpe:2.3:a:f5:big-ip_application_security_manager:*:*:*:*:*:*:*:*
f5 big-ip_ddos_hybrid_defender >= 12.1.0, < 12.1.5.3 cpe:2.3:a:f5:big-ip_ddos_hybrid_defender:*:*:*:*:*:*:*:*
f5 big-ip_ddos_hybrid_defender >= 13.1.0, < 13.1.3.6 cpe:2.3:a:f5:big-ip_ddos_hybrid_defender:*:*:*:*:*:*:*:*
f5 big-ip_ddos_hybrid_defender >= 14.1.0, < 14.1.4 cpe:2.3:a:f5:big-ip_ddos_hybrid_defender:*:*:*:*:*:*:*:*
f5 big-ip_ddos_hybrid_defender >= 15.1.0, < 15.1.2.1 cpe:2.3:a:f5:big-ip_ddos_hybrid_defender:*:*:*:*:*:*:*:*
f5 big-ip_ddos_hybrid_defender >= 16.0.0, < 16.0.1.1 cpe:2.3:a:f5:big-ip_ddos_hybrid_defender:*:*:*:*:*:*:*:*
f5 big-ip_domain_name_system >= 12.1.0, < 12.1.5.3 cpe:2.3:a:f5:big-ip_domain_name_system:*:*:*:*:*:*:*:*
f5 big-ip_domain_name_system >= 13.1.0, < 13.1.3.6 cpe:2.3:a:f5:big-ip_domain_name_system:*:*:*:*:*:*:*:*
f5 big-ip_domain_name_system >= 14.1.0, < 14.1.4 cpe:2.3:a:f5:big-ip_domain_name_system:*:*:*:*:*:*:*:*
f5 big-ip_domain_name_system >= 15.1.0, < 15.1.2.1 cpe:2.3:a:f5:big-ip_domain_name_system:*:*:*:*:*:*:*:*
f5 big-ip_domain_name_system >= 16.0.0, < 16.0.1.1 cpe:2.3:a:f5:big-ip_domain_name_system:*:*:*:*:*:*:*:*
f5 big-ip_fraud_protection_service >= 12.1.0, < 12.1.5.3 cpe:2.3:a:f5:big-ip_fraud_protection_service:*:*:*:*:*:*:*:*
f5 big-ip_fraud_protection_service >= 13.1.0, < 13.1.3.6 cpe:2.3:a:f5:big-ip_fraud_protection_service:*:*:*:*:*:*:*:*
f5 big-ip_fraud_protection_service >= 14.1.0, < 14.1.4 cpe:2.3:a:f5:big-ip_fraud_protection_service:*:*:*:*:*:*:*:*
f5 big-ip_fraud_protection_service >= 15.1.0, < 15.1.2.1 cpe:2.3:a:f5:big-ip_fraud_protection_service:*:*:*:*:*:*:*:*
f5 big-ip_fraud_protection_service >= 16.0.0, < 16.0.1.1 cpe:2.3:a:f5:big-ip_fraud_protection_service:*:*:*:*:*:*:*:*
f5 big-ip_global_traffic_manager >= 12.1.0, < 12.1.5.3 cpe:2.3:a:f5:big-ip_global_traffic_manager:*:*:*:*:*:*:*:*
f5 big-ip_global_traffic_manager >= 13.1.0, < 13.1.3.6 cpe:2.3:a:f5:big-ip_global_traffic_manager:*:*:*:*:*:*:*:*
f5 big-ip_global_traffic_manager >= 14.1.0, < 14.1.4 cpe:2.3:a:f5:big-ip_global_traffic_manager:*:*:*:*:*:*:*:*
f5 big-ip_global_traffic_manager >= 15.1.0, < 15.1.2.1 cpe:2.3:a:f5:big-ip_global_traffic_manager:*:*:*:*:*:*:*:*
f5 big-ip_global_traffic_manager >= 16.0.0, < 16.0.1.1 cpe:2.3:a:f5:big-ip_global_traffic_manager:*:*:*:*:*:*:*:*
f5 big-ip_link_controller >= 12.1.0, < 12.1.5.3 cpe:2.3:a:f5:big-ip_link_controller:*:*:*:*:*:*:*:*
f5 big-ip_link_controller >= 13.1.0, < 13.1.3.6 cpe:2.3:a:f5:big-ip_link_controller:*:*:*:*:*:*:*:*
f5 big-ip_link_controller >= 14.1.0, < 14.1.4 cpe:2.3:a:f5:big-ip_link_controller:*:*:*:*:*:*:*:*
f5 big-ip_link_controller >= 15.1.0, < 15.1.2.1 cpe:2.3:a:f5:big-ip_link_controller:*:*:*:*:*:*:*:*
f5 big-ip_link_controller >= 16.0.0, < 16.0.1.1 cpe:2.3:a:f5:big-ip_link_controller:*:*:*:*:*:*:*:*
f5 big-ip_local_traffic_manager >= 12.1.0, < 12.1.5.3 cpe:2.3:a:f5:big-ip_local_traffic_manager:*:*:*:*:*:*:*:*
f5 big-ip_local_traffic_manager >= 13.1.0, < 13.1.3.6 cpe:2.3:a:f5:big-ip_local_traffic_manager:*:*:*:*:*:*:*:*
f5 big-ip_local_traffic_manager >= 14.1.0, < 14.1.4 cpe:2.3:a:f5:big-ip_local_traffic_manager:*:*:*:*:*:*:*:*
f5 big-ip_local_traffic_manager >= 15.1.0, < 15.1.2.1 cpe:2.3:a:f5:big-ip_local_traffic_manager:*:*:*:*:*:*:*:*
f5 big-ip_local_traffic_manager >= 16.0.0, < 16.0.1.1 cpe:2.3:a:f5:big-ip_local_traffic_manager:*:*:*:*:*:*:*:*
f5 big-ip_policy_enforcement_manager >= 12.1.0, < 12.1.5.3 cpe:2.3:a:f5:big-ip_policy_enforcement_manager:*:*:*:*:*:*:*:*
f5 big-ip_policy_enforcement_manager >= 13.1.0, < 13.1.3.6 cpe:2.3:a:f5:big-ip_policy_enforcement_manager:*:*:*:*:*:*:*:*
f5 big-ip_policy_enforcement_manager >= 14.1.0, < 14.1.4 cpe:2.3:a:f5:big-ip_policy_enforcement_manager:*:*:*:*:*:*:*:*
f5 big-ip_policy_enforcement_manager >= 15.1.0, < 15.1.2.1 cpe:2.3:a:f5:big-ip_policy_enforcement_manager:*:*:*:*:*:*:*:*
f5 big-ip_policy_enforcement_manager >= 16.0.0, < 16.0.1.1 cpe:2.3:a:f5:big-ip_policy_enforcement_manager:*:*:*:*:*:*:*:*
f5 ssl_orchestrator >= 12.1.0, < 12.1.5.3 cpe:2.3:a:f5:ssl_orchestrator:*:*:*:*:*:*:*:*
f5 ssl_orchestrator >= 13.1.0, < 13.1.3.6 cpe:2.3:a:f5:ssl_orchestrator:*:*:*:*:*:*:*:*
f5 ssl_orchestrator >= 14.1.0, < 14.1.4 cpe:2.3:a:f5:ssl_orchestrator:*:*:*:*:*:*:*:*
f5 ssl_orchestrator >= 15.1.0, < 15.1.2.1 cpe:2.3:a:f5:ssl_orchestrator:*:*:*:*:*:*:*:*
f5 ssl_orchestrator >= 16.0.0, < 16.0.1.1 cpe:2.3:a:f5:ssl_orchestrator:*:*:*:*:*:*:*:*

References for CVE-2021-22991

cvelogic Threat Intelligence