Risk Letters

Exploited vulnerability

CVE-2025-53521

TLP:CLEAR

F5 BIG-IP Stack-Based Buffer Overflow Vulnerability

F5 BIG-IP APM contains a stack-based buffer overflow vulnerability that could allow a threat actor to achieve remote code execution.

Facts

  • Vendor: F5
  • Product: BIG-IP
  • CVSS: 9.3
  • EPSS (probability of exploitation within 30 days): 2.3 %
  • On CISA's Known Exploited Vulnerabilities list since: 27 March 2026
  • First known exploitation: 27 March 2026
  • CISA's deadline for US federal agencies: 30 March 2026
  • Weakness: CWE-121
  • First seen by Risk Letters: 27 March 2026

Members see which Nordic sectors the flaw hits, and what to do about it.

Get the full brief

Data: NVD (public domain), CISA KEV, FIRST EPSS, MITRE ATT&CK, AlienVault OTX. NVD