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Known Exploited Vulnerability
9.8
CRITICAL CVSS 3.1
CVE-2021-22991
F5 BIG-IP Traffic Management Microkernel Buffer Overflow - [Actively Exploited]
Description

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.

INFO

Published Date :

March 31, 2021, 6:15 p.m.

Last Modified :

Oct. 27, 2025, 5:06 p.m.

Remotely Exploit :

Yes !

Source :

[email protected]
CISA Notification
CISA KEV (Known Exploited Vulnerabilities)

For the benefit of the cybersecurity community and network defenders—and to help every organization better manage vulnerabilities and keep pace with threat activity—CISA maintains the authoritative source of vulnerabilities that have been exploited in the wild.

Description :

The Traffic Management Microkernel of BIG-IP ASM Risk Engine has a buffer overflow vulnerability, leading to a bypassing of URL-based access controls.

Required Action :

Apply updates per vendor instructions.

Notes :

https://nvd.nist.gov/vuln/detail/CVE-2021-22991

Affected Products

The following products are affected by CVE-2021-22991 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 F5 big-ip_access_policy_manager
2 F5 big-ip_advanced_firewall_manager
3 F5 big-ip_analytics
4 F5 big-ip_application_acceleration_manager
5 F5 big-ip_application_security_manager
6 F5 big-ip_domain_name_system
7 F5 big-ip_fraud_protection_service
8 F5 big-ip_global_traffic_manager
9 F5 big-ip_link_controller
10 F5 big-ip_local_traffic_manager
11 F5 big-ip_policy_enforcement_manager
12 F5 big-ip_advanced_web_application_firewall
13 F5 big-ip_ddos_hybrid_defender
14 F5 ssl_orchestrator
: Total Affected Vendor : 1 | Products : 14
CVSS Scores
The Common Vulnerability Scoring System is a standardized framework for assessing the severity of vulnerabilities in software and systems. We collect and displays CVSS scores from various sources for each CVE.
Score Version Severity Vector Exploitability Score Impact Score Source
CVSS 2.0 MEDIUM [email protected]
CVSS 3.1 CRITICAL [email protected]
CVSS 3.1 CRITICAL 134c704f-9b21-4f2e-91b3-4a467353bcc0
Solution
This information is provided by the 3rd party feeds.
  • Upgrade to one of the non-vulnerable versions listed in the F5 Solution K56715231.
Public PoC/Exploit Available at Github

CVE-2021-22991 has a 5 public PoC/Exploit available at Github. Go to the Public Exploits tab to see the list.

References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2021-22991.

URL Resource
https://support.f5.com/csp/article/K56715231 Vendor Advisory
https://support.f5.com/csp/article/K56715231 Vendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-22991 US Government Resource
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2021-22991 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2021-22991 weaknesses.

CAPEC-8: Buffer Overflow in an API Call Buffer Overflow in an API Call CAPEC-9: Buffer Overflow in Local Command-Line Utilities Buffer Overflow in Local Command-Line Utilities CAPEC-10: Buffer Overflow via Environment Variables Buffer Overflow via Environment Variables CAPEC-14: Client-side Injection-induced Buffer Overflow Client-side Injection-induced Buffer Overflow CAPEC-24: Filter Failure through Buffer Overflow Filter Failure through Buffer Overflow CAPEC-42: MIME Conversion MIME Conversion CAPEC-44: Overflow Binary Resource File Overflow Binary Resource File CAPEC-45: Buffer Overflow via Symbolic Links Buffer Overflow via Symbolic Links CAPEC-46: Overflow Variables and Tags Overflow Variables and Tags CAPEC-47: Buffer Overflow via Parameter Expansion Buffer Overflow via Parameter Expansion CAPEC-100: Overflow Buffers Overflow Buffers CAPEC-123: Buffer Manipulation Buffer Manipulation

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

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Updated: 4 years, 1 month ago
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Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2021-22991 vulnerability anywhere in the article.

Results are limited to the first 20 news articles due to potential performance issues.

The following table lists the changes that have been made to the CVE-2021-22991 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • Modified Analysis by [email protected]

    Oct. 27, 2025

    Action Type Old Value New Value
    Added Reference Type CISA-ADP: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-22991 Types: US Government Resource
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Oct. 22, 2025

    Action Type Old Value New Value
    Added Reference https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-22991
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Oct. 21, 2025

    Action Type Old Value New Value
    Removed Reference https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-22991
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Oct. 21, 2025

    Action Type Old Value New Value
    Added Reference https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-22991
  • Modified Analysis by [email protected]

    Apr. 02, 2025

    Action Type Old Value New Value
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Jan. 29, 2025

    Action Type Old Value New Value
    Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    Added CWE CWE-119
  • CVE Modified by af854a3a-2127-422b-91ae-364da2661108

    Nov. 21, 2024

    Action Type Old Value New Value
    Added Reference https://support.f5.com/csp/article/K56715231
  • CVE Modified by [email protected]

    May. 14, 2024

    Action Type Old Value New Value
  • CWE Remap by [email protected]

    Jul. 12, 2022

    Action Type Old Value New Value
    Changed CWE CWE-120 CWE-20
  • Initial Analysis by [email protected]

    Apr. 05, 2021

    Action Type Old Value New Value
    Added CVSS V2 NIST (AV:N/AC:M/Au:N/C:P/I:P/A:P)
    Added CVSS V3.1 NIST AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    Changed Reference Type https://support.f5.com/csp/article/K56715231 No Types Assigned https://support.f5.com/csp/article/K56715231 Vendor Advisory
    Added CWE NIST CWE-120
    Added CPE Configuration OR *cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:* versions from (including) 12.1.0 up to (excluding) 12.1.5.3 *cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:* versions from (including) 13.1.0 up to (excluding) 13.1.3.6 *cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:* versions from (including) 14.1.0 up to (excluding) 14.1.4 *cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:* versions from (including) 15.1.0 up to (excluding) 15.1.2.1 *cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:* versions from (including) 16.0.0 up to (excluding) 16.0.1.1 *cpe:2.3:a:f5:big-ip_advanced_firewall_manager:*:*:*:*:*:*:*:* versions from (including) 12.1.0 up to (excluding) 12.1.5.3 *cpe:2.3:a:f5:big-ip_advanced_firewall_manager:*:*:*:*:*:*:*:* versions from (including) 13.1.0 up to (excluding) 13.1.3.6 *cpe:2.3:a:f5:big-ip_advanced_firewall_manager:*:*:*:*:*:*:*:* versions from (including) 14.1.0 up to (excluding) 14.1.4 *cpe:2.3:a:f5:big-ip_advanced_firewall_manager:*:*:*:*:*:*:*:* versions from (including) 15.1.0 up to (excluding) 15.1.2.1 *cpe:2.3:a:f5:big-ip_advanced_firewall_manager:*:*:*:*:*:*:*:* versions from (including) 16.0.0 up to (excluding) 16.0.1.1 *cpe:2.3:a:f5:big-ip_advanced_web_application_firewall:*:*:*:*:*:*:*:* versions from (including) 12.1.0 up to (excluding) 12.1.5.3 *cpe:2.3:a:f5:big-ip_advanced_web_application_firewall:*:*:*:*:*:*:*:* versions from (including) 13.1.0 up to (excluding) 13.1.3.6 *cpe:2.3:a:f5:big-ip_advanced_web_application_firewall:*:*:*:*:*:*:*:* versions from (including) 14.1.0 up to (excluding) 14.1.4 *cpe:2.3:a:f5:big-ip_advanced_web_application_firewall:*:*:*:*:*:*:*:* versions from (including) 15.1.0 up to (excluding) 15.1.2.1 *cpe:2.3:a:f5:big-ip_advanced_web_application_firewall:*:*:*:*:*:*:*:* versions from (including) 16.0.0 up to (excluding) 16.0.1.1 *cpe:2.3:a:f5:big-ip_analytics:*:*:*:*:*:*:*:* versions from (including) 12.1.0 up to (excluding) 12.1.5.3 *cpe:2.3:a:f5:big-ip_analytics:*:*:*:*:*:*:*:* versions from (including) 13.1.0 up to (excluding) 13.1.3.6 *cpe:2.3:a:f5:big-ip_analytics:*:*:*:*:*:*:*:* versions from (including) 14.1.0 up to (excluding) 14.1.4 *cpe:2.3:a:f5:big-ip_analytics:*:*:*:*:*:*:*:* versions from (including) 15.1.0 up to (excluding) 15.1.2.1 *cpe:2.3:a:f5:big-ip_analytics:*:*:*:*:*:*:*:* versions from (including) 16.0.0 up to (excluding) 16.0.1.1 *cpe:2.3:a:f5:big-ip_application_acceleration_manager:*:*:*:*:*:*:*:* versions from (including) 12.1.0 up to (excluding) 12.1.5.3 *cpe:2.3:a:f5:big-ip_application_acceleration_manager:*:*:*:*:*:*:*:* versions from (including) 13.1.0 up to (excluding) 13.1.3.6 *cpe:2.3:a:f5:big-ip_application_acceleration_manager:*:*:*:*:*:*:*:* versions from (including) 14.1.0 up to (excluding) 14.1.4 *cpe:2.3:a:f5:big-ip_application_acceleration_manager:*:*:*:*:*:*:*:* versions from (including) 15.1.0 up to (excluding) 15.1.2.1 *cpe:2.3:a:f5:big-ip_application_acceleration_manager:*:*:*:*:*:*:*:* versions from (including) 16.0.0 up to (excluding) 16.0.1.1 *cpe:2.3:a:f5:big-ip_application_security_manager:*:*:*:*:*:*:*:* versions from (including) 12.1.0 up to (excluding) 12.1.5.3 *cpe:2.3:a:f5:big-ip_application_security_manager:*:*:*:*:*:*:*:* versions from (including) 13.1.0 up to (excluding) 13.1.3.6 *cpe:2.3:a:f5:big-ip_application_security_manager:*:*:*:*:*:*:*:* versions from (including) 14.1.0 up to (excluding) 14.1.4 *cpe:2.3:a:f5:big-ip_application_security_manager:*:*:*:*:*:*:*:* versions from (including) 15.1.0 up to (excluding) 15.1.2.1 *cpe:2.3:a:f5:big-ip_application_security_manager:*:*:*:*:*:*:*:* versions from (including) 16.0.0 up to (excluding) 16.0.1.1 *cpe:2.3:a:f5:big-ip_ddos_hybrid_defender:*:*:*:*:*:*:*:* versions from (including) 12.1.0 up to (excluding) 12.1.5.3 *cpe:2.3:a:f5:big-ip_ddos_hybrid_defender:*:*:*:*:*:*:*:* versions from (including) 13.1.0 up to (excluding) 13.1.3.6 *cpe:2.3:a:f5:big-ip_ddos_hybrid_defender:*:*:*:*:*:*:*:* versions from (including) 14.1.0 up to (excluding) 14.1.4 *cpe:2.3:a:f5:big-ip_ddos_hybrid_defender:*:*:*:*:*:*:*:* versions from (including) 15.1.0 up to (excluding) 15.1.2.1 *cpe:2.3:a:f5:big-ip_ddos_hybrid_defender:*:*:*:*:*:*:*:* versions from (including) 16.0.0 up to (excluding) 16.0.1.1 *cpe:2.3:a:f5:big-ip_domain_name_system:*:*:*:*:*:*:*:* versions from (including) 12.1.0 up to (excluding) 12.1.5.3 *cpe:2.3:a:f5:big-ip_domain_name_system:*:*:*:*:*:*:*:* versions from (including) 13.1.0 up to (excluding) 13.1.3.6 *cpe:2.3:a:f5:big-ip_domain_name_system:*:*:*:*:*:*:*:* versions from (including) 14.1.0 up to (excluding) 14.1.4 *cpe:2.3:a:f5:big-ip_domain_name_system:*:*:*:*:*:*:*:* versions from (including) 15.1.0 up to (excluding) 15.1.2.1 *cpe:2.3:a:f5:big-ip_domain_name_system:*:*:*:*:*:*:*:* versions from (including) 16.0.0 up to (excluding) 16.0.1.1 *cpe:2.3:a:f5:big-ip_fraud_protection_service:*:*:*:*:*:*:*:* versions from (including) 12.1.0 up to (excluding) 12.1.5.3 *cpe:2.3:a:f5:big-ip_fraud_protection_service:*:*:*:*:*:*:*:* versions from (including) 13.1.0 up to (excluding) 13.1.3.6 *cpe:2.3:a:f5:big-ip_fraud_protection_service:*:*:*:*:*:*:*:* versions from (including) 14.1.0 up to (excluding) 14.1.4 *cpe:2.3:a:f5:big-ip_fraud_protection_service:*:*:*:*:*:*:*:* versions from (including) 15.1.0 up to (excluding) 15.1.2.1 *cpe:2.3:a:f5:big-ip_fraud_protection_service:*:*:*:*:*:*:*:* versions from (including) 16.0.0 up to (excluding) 16.0.1.1 *cpe:2.3:a:f5:big-ip_global_traffic_manager:*:*:*:*:*:*:*:* versions from (including) 12.1.0 up to (excluding) 12.1.5.3 *cpe:2.3:a:f5:big-ip_global_traffic_manager:*:*:*:*:*:*:*:* versions from (including) 13.1.0 up to (excluding) 13.1.3.6 *cpe:2.3:a:f5:big-ip_global_traffic_manager:*:*:*:*:*:*:*:* versions from (including) 14.1.0 up to (excluding) 14.1.4 *cpe:2.3:a:f5:big-ip_global_traffic_manager:*:*:*:*:*:*:*:* versions from (including) 15.1.0 up to (excluding) 15.1.2.1 *cpe:2.3:a:f5:big-ip_global_traffic_manager:*:*:*:*:*:*:*:* versions from (including) 16.0.0 up to (excluding) 16.0.1.1 *cpe:2.3:a:f5:big-ip_link_controller:*:*:*:*:*:*:*:* versions from (including) 12.1.0 up to (excluding) 12.1.5.3 *cpe:2.3:a:f5:big-ip_link_controller:*:*:*:*:*:*:*:* versions from (including) 13.1.0 up to (excluding) 13.1.3.6 *cpe:2.3:a:f5:big-ip_link_controller:*:*:*:*:*:*:*:* versions from (including) 14.1.0 up to (excluding) 14.1.4 *cpe:2.3:a:f5:big-ip_link_controller:*:*:*:*:*:*:*:* versions from (including) 15.1.0 up to (excluding) 15.1.2.1 *cpe:2.3:a:f5:big-ip_link_controller:*:*:*:*:*:*:*:* versions from (including) 16.0.0 up to (excluding) 16.0.1.1 *cpe:2.3:a:f5:big-ip_local_traffic_manager:*:*:*:*:*:*:*:* versions from (including) 12.1.0 up to (excluding) 12.1.5.3 *cpe:2.3:a:f5:big-ip_local_traffic_manager:*:*:*:*:*:*:*:* versions from (including) 13.1.0 up to (excluding) 13.1.3.6 *cpe:2.3:a:f5:big-ip_local_traffic_manager:*:*:*:*:*:*:*:* versions from (including) 14.1.0 up to (excluding) 14.1.4 *cpe:2.3:a:f5:big-ip_local_traffic_manager:*:*:*:*:*:*:*:* versions from (including) 15.1.0 up to (excluding) 15.1.2.1 *cpe:2.3:a:f5:big-ip_local_traffic_manager:*:*:*:*:*:*:*:* versions from (including) 16.0.0 up to (excluding) 16.0.1.1 *cpe:2.3:a:f5:big-ip_policy_enforcement_manager:*:*:*:*:*:*:*:* versions from (including) 12.1.0 up to (excluding) 12.1.5.3 *cpe:2.3:a:f5:big-ip_policy_enforcement_manager:*:*:*:*:*:*:*:* versions from (including) 13.1.0 up to (excluding) 13.1.3.6 *cpe:2.3:a:f5:big-ip_policy_enforcement_manager:*:*:*:*:*:*:*:* versions from (including) 14.1.0 up to (excluding) 14.1.4 *cpe:2.3:a:f5:big-ip_policy_enforcement_manager:*:*:*:*:*:*:*:* versions from (including) 15.1.0 up to (excluding) 15.1.2.1 *cpe:2.3:a:f5:big-ip_policy_enforcement_manager:*:*:*:*:*:*:*:* versions from (including) 16.0.0 up to (excluding) 16.0.1.1 *cpe:2.3:a:f5:ssl_orchestrator:*:*:*:*:*:*:*:* versions from (including) 12.1.0 up to (excluding) 12.1.5.3 *cpe:2.3:a:f5:ssl_orchestrator:*:*:*:*:*:*:*:* versions from (including) 13.1.0 up to (excluding) 13.1.3.6 *cpe:2.3:a:f5:ssl_orchestrator:*:*:*:*:*:*:*:* versions from (including) 14.1.0 up to (excluding) 14.1.4 *cpe:2.3:a:f5:ssl_orchestrator:*:*:*:*:*:*:*:* versions from (including) 15.1.0 up to (excluding) 15.1.2.1 *cpe:2.3:a:f5:ssl_orchestrator:*:*:*:*:*:*:*:* versions from (including) 16.0.0 up to (excluding) 16.0.1.1
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
Vulnerability Scoring Details
Base CVSS Score: 9.8
Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality Impact
Integrity Impact
Availability Impact
Base CVSS Score: 6.8
Access Vector
Access Complexity
Authentication
Confidentiality Impact
Integrity Impact
Availability Impact
Exploit Prediction

EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days.

66.26 }} -4.52%

score

0.98441

percentile