critical Known exploitedREV. 01

CVE-2025-53521F5 BIG-IP APM — stack overflow in the access policy to RCE

When an Access Policy Manager (APM) policy is attached to a virtual server on F5's traffic manager, specific crafted traffic overflows a stack buffer and hands the sender remote code execution on the appliance.

YOUR NEXT MOVE

Patch per F5 article K000156741 now; builds past end of technical support were never evaluated, so treat those as affected and plan their replacement.

Read the risk

THE VITAL STATS
CVSS score
9.3/ 10
CVSS v4.0
EPSS probability
2%
Likelihood of exploitation
Attack complexity
Low
Conditions needed to exploit
Known exploited
Yes — CISA KEV
CVE published
2025-10-15
Added to KEV
2026-03-27
Exploit published
Not recorded
Confidence
high
Kill chain
initial access
MITRE ATT&CK
T1190
Severity
critical

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attacker needsNetwork reach to a virtual server carrying an access policy; no credentials needed.

Behind the card

3 REFERENCES
Field-level provenanceTRACE THE SOURCES +

Which source supports each field, when it was retrieved, and who extracted it.

FieldsSourceRetrievedExtractorConfidence
cvss, exploitation.attack_complexity, exploitation.exploit_available, references, published_atnvd.nist.gov2026-09-24scrty-crds-pipeline/0.1high
exploitation.known_exploited, exploitation.kev_addedcisa.gov2026-09-24scrty-crds-pipeline/0.1high
epssapi.first.org2026-09-24scrty-crds-pipeline/0.1high
title, summary, severity, remediation, mitre_attack, kill_chain, recommended_action, confidence, tags, exploitation.prerequisitesnvd.nist.gov2026-09-24claude-codehigh

Printing history

THE RECORD
  1. r1Initial base card

First printing. This card has not been reprinted since publication.

crds:cve-2025-53521 · CRDS 0.1 · Issued 2026-09-24