THE Known Exploited Vulnerabilities (KEV) catalog lists CVE-2025-53521 as an F5 BIG-IP unspecified vulnerability that could allow a threat actor to achieve remote code execution. It notes that the vulnerability is currently unknown whether it is used in ransomware campaigns. Action recommended includes applying mitigations per vendor instructions, following relevant cloud service guidance, or discontinuing use of the product if mitigations are unavailable.
The entry shows a Date Added of 27 March 2026 and a Due Date of 30 March 2026. Additional notes advise adherence to F5 guidelines to assess exposure and mitigate risks and to check for signs of potential compromise on all internet-facing F5 products affected by this vulnerability, with further information linked to F5 support articles and the NVD page for CVE-2025-53521.