F5 BIG-IP Stack-Based Buffer Overflow Vulnerability (CVE-2025-53521)
F5 BIG-IP APM contains a stack-based buffer overflow vulnerability that could allow a threat actor to achieve remote code execution.
A remote attacker, without authentication, can achieve full data confidentiality loss, arbitrary modification of data, complete denial of service or system unavailability. Federal agencies are required to remediate by 2026-03-30 under CISA BOD 22-01.
This is a Stack-based Buffer Overflow (CWE-121) vulnerability in F5 BIG-IP. When a BIG-IP APM access policy is configured on a virtual server, specific malicious traffic can lead to Remote Code Execution (RCE). Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated. Exploitation requires remote network access, low attack complexity, no authentication required, and no user interaction required.
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Phishing link
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Malicious file
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Server compromised
Probably yes if any of these apply:
CISA added this CVE to the Known Exploited Vulnerabilities catalog on 2026-03-27 based on evidence of active exploitation in the wild. Federal agencies required to remediate by 2026-03-30.
Get the fix
Apply the fixed package from your vendor. The advisory lists affected versions and the exact fixed build.
↗ Vendor advisoryManual remediation steps
Apply the Vendor Patch
This vulnerability is in the CISA Known Exploited Vulnerabilities catalog — apply the vendor's security update as soon as possible.
CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
References
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References