How severe is CVE-2025-53521?

CVE-2025-53521 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2025-53521 being actively exploited?

Yes. CVE-2025-53521 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2026-03-27, which means active exploitation has been confirmed. It should be prioritised for remediation.

What products are affected by CVE-2025-53521?

CVE-2025-53521 affects F5 Big-ip Access Policy Manager. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-53521?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.

Does CVE-2025-53521 have an EU (EUVD) identifier?

Yes. CVE-2025-53521 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-34630. It is also flagged as exploited in the EUVD (since 2026-03-27).

When was CVE-2025-53521 published?

CVE-2025-53521 was published on 2025-10-15 and last updated on 2026-06-17.

CVE-2025-53521

CVE-2025-53521 is a critical-severity vulnerability in F5 Big-ip Access Policy Manager with a CVSS 3.x base score of 9.8. It is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming it has been exploited in the wild (added 2026-03-27). The underlying weakness is classified as CWE-121.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v4: 9.3
EPSS exploit prediction: 2% (81st percentile)
Actively exploited: Yes — listed in CISA KEV (added 2026-03-27)
EU (EUVD) id: EUVD-2025-34630
EU exploitation: Flagged exploited in the ENISA EU Vulnerability Database (since 2026-03-27)
Weakness: CWE-121
Affected product: F5 Big-ip Access Policy Manager
Published: 2025-10-15
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2025-53521?: 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.
How severe is CVE-2025-53521?: CVE-2025-53521 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2025-53521 being actively exploited?: Yes. CVE-2025-53521 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2026-03-27, which means active exploitation has been confirmed. It should be prioritised for remediation.
What products are affected by CVE-2025-53521?: CVE-2025-53521 affects F5 Big-ip Access Policy Manager. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-53521?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.
Does CVE-2025-53521 have an EU (EUVD) identifier?: Yes. CVE-2025-53521 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-34630. It is also flagged as exploited in the EUVD (since 2026-03-27).
When was CVE-2025-53521 published?: CVE-2025-53521 was published on 2025-10-15 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:f5:big-ip_access_policy_manager:*:*:*:*:*:*:*:*

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