CISA KEV · Known exploitedCritical

CVE-2025-53521

F5 BIG-IP

When a BIG-IP APM access policy is configured on a virtual server, specific malicious traffic can lead to Remote Code Execution (RCE). Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

CVSS
9.3
EPSS
2.21%
80.9% percentile
CISA KEV
Listed
Published
2025.10.15
PRIORITY ASSESSMENT

Immediate review

CISA has listed this vulnerability in the Known Exploited Vulnerabilities catalog.

Known exploitationConfirmed by CISA KEV
Exploit probability2.21%
Technical severityCVSS 9.3

Vulnerability overview

When a BIG-IP APM access policy is configured on a virtual server, specific malicious traffic can lead to Remote Code Execution (RCE). Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Affected product and versions

Product
F5 BIG-IP
Affected versions
17.5.0, 17.1.0, 16.1.0, 15.1.0, >= 15.1.0 < 15.1.10.8, >= 16.1.0 < 16.1.6.1, >= 17.1.0 < 17.1.3, >= 17.5.0 < 17.5.1.3
Fixed versions
15.1.10.8, 16.1.6.1, 17.1.3, 17.5.1.3

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
CISA required action

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Due date: 2026.03.30
  1. 1
    Identify

    Confirm that F5 BIG-IP and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
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
CWE
CWE-121
KEV added
2026.03.27
Ransomware use
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