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CVE-2025-53521 lands in CISA's KEV catalog: F5 BIG-IP RCE under active exploitation

CISA added CVE-2025-53521 to the Known Exploited Vulnerabilities catalog on 27 March 2026 after confirming active exploitation of this CVSS 9.8 RCE in F5 BIG-IP. Affected versions span three major branches.