CVE-2021-22991
CriticalExploitedPublic exploitOn 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…
Published Mar 31, 2021 · Updated Oct 27, 2025
Key Facts
Patch immediately- CVE-2021-22991 is a critical-severity vulnerability (CVSS 9.8 v3.1) affecting Big-Ip Access Policy Manager (F5), Big-Ip Advanced Firewall Manager (F5), Big-Ip Advanced Web Application Firewall (F5) and 12 more products.
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jun 1, 2021. Public exploit code is available.
- EPSS estimates a 61% probability of exploitation in the next 30 days.
- Fixed versions are available, including Big-Ip Access Policy Manager 12.1.5.3, Big-Ip Advanced Firewall Manager 12.1.5.3, Big-Ip Advanced Web Application Firewall 12.1.5.3.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
9.8
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
61%
Higher than 99.1% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2021-22991 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Jan 18, 2022 | Feb 1, 2022 | Not reported |
| Industry KEV feed | Jun 1, 2021 | Feb 1, 2022 | Not reported |
| CIRCL KEV | Jan 18, 2022 | Feb 1, 2022 | Not reported |
| ENISA EUVD | Jan 18, 2022 | n/a | Not reported |
Required action: Apply updates per vendor instructions.
Affected Products
15 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Big-Ip Access Policy ManagerF5 | See advisory | 12.1.5.3 |
| Big-Ip Advanced Firewall ManagerF5 | See advisory | 12.1.5.3 |
| Big-Ip Advanced Web Application FirewallF5 | See advisory | 12.1.5.3 |
| Big-Ip AnalyticsF5 | See advisory | 12.1.5.3 |
| Big-Ip Application Acceleration ManagerF5 | See advisory | 12.1.5.3 |
Patched Releases
Big-Ip Access Policy Manager
12.1.5.3
Big-Ip Advanced Firewall Manager
12.1.5.3
Big-Ip Advanced Web Application Firewall
12.1.5.3
Big-Ip Analytics
12.1.5.3
Big-Ip Application Acceleration Manager
12.1.5.3
Big-Ip Application Security Manager
12.1.5.3
Big-Ip Ddos Hybrid Defender
12.1.5.3
Big-Ip Domain Name System
12.1.5.3
Big-Ip Fraud Protection Service
12.1.5.3
Big-Ip Global Traffic Manager
12.1.5.3
Big-Ip Link Controller
12.1.5.3
Big-Ip Local Traffic Manager
12.1.5.3
Big-Ip Policy Enforcement Manager
12.1.5.3
SSL Orchestrator
12.1.5.3
Timeline
Publicly disclosed
Mar 31, 2021
Added to Industry KEV feed
Jun 1, 2021
Added to CISA KEV
Jan 18, 2022
Added to CIRCL KEV
Jan 18, 2022
Added to ENISA EUVD
Jan 18, 2022
Last updated
Oct 27, 2025
Weakness Type
- CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer
References
FAQ
Common Questions.
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…
Affected: Big-Ip Access Policy Manager (F5); Big-Ip Advanced Firewall Manager (F5); Big-Ip Advanced Web Application Firewall (F5), among others. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jun 1, 2021.
Yes. It was added on Jan 18, 2022 with a federal remediation due date of Feb 1, 2022.
Public exploit code is available.
Fixed versions are available, including Big-Ip Access Policy Manager 12.1.5.3, Big-Ip Advanced Firewall Manager 12.1.5.3, Big-Ip Advanced Web Application Firewall 12.1.5.3.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
Is CVE-2021-22991 Running On Your Attack Surface?
Brandefense maps vulnerabilities like this one to your internet-facing assets and tells you exactly where to patch.
Request A Demo