CVE-2025-53521

F5 — F5 BIG-IP Stack-Based Buffer Overflow Vulnerability

CISA KEV · in the CISA KEV catalog since 2026-03-27

What EVULNABLE says

EVULNABLE Risk · priority 75/100 Urgent Raised to the floor for a confirmed exploited vulnerability. Intelligence coverage 75/90 — no pre-patch disclosure data
Overdue by 5 monthsCISA KEVActively Exploited

Why it matters: Listed in the CISA KEV catalog, and Confirmed exploitation in the wild.

Patch This Cycle

The priority band answers “how soon”, not “how bad” — see Methodology for what it weighs and where it abstains.

The evidence behind it

Published measurements for CVE-2025-53521
MeasureValueSource
CVSS base score 9.3 NVD
FIRST EPSS 0.022 (81.4th pctl) FIRST
Actively exploited Confirmed CISA KEV
Ransomware campaign use Unknown or none CISA KEV
CISA remediation deadline 2026-03-30 — Overdue by 5 months CISA KEV
Intelligence coverage 75/90 — no pre-patch disclosure data

What CISA says to do

This page is an opinion about urgency. Where it and a source of record disagree, the source of record is the record.

NVD ↗ CISA KEV ↗ Vendor Advisory ↗