CVE-2021-22991
Published: January 18, 2022
Official 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.
CISA KEV Advisory
F5 BIG-IP Traffic Management Microkernel Buffer Overflow
The Traffic Management Microkernel of BIG-IP ASM Risk Engine has a buffer overflow vulnerability, leading to a bypassing of URL-based access controls.
Apply updates per vendor instructions.
Risk Analysis
The Traffic Management Microkernel of BIG-IP ASM Risk Engine has a buffer overflow vulnerability that can lead to bypassing URL-based access controls. With an EPSS score of 0.73095 and confirmed exploitation by CISA (is_in_kev: true), this is a high-priority vulnerability that is actively being exploited.
This vulnerability is actively exploited in the wild, indicating a severe and immediate risk. Its inclusion in CISA's KEV confirms its active use by attackers.
F5 BIG-IP ASM Risk Engine users should apply the latest security updates to address this buffer overflow. Regularly review and update access control policies to ensure their effectiveness.
Technical Analysis
CVE-2021-22991 requires local access, meaning attackers must already have a foothold on the target system.
Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
CISA has added CVE-2021-22991 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.
Exploit & PoC Resources
All References (1)
Quick Facts
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-22991 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
- !CISA KEV: Federal agencies must patch per BOD 22-01 timeline
- !Active exploitation confirmed — treat as P1