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.
do firstApply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Can a WAF block it? No. This is a stack buffer overflow. Generic WAF rules do not recognise the input that triggers it; only a rule written for this specific CVE can, and only if the triggering request has a recognisable shape.
Also consider: patch
Based on the weakness type only; no CVE-specific evidence yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Is CVE-2025-53521 being exploited?
Yes. CVE-2025-53521 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2025-53521?
CVE-2025-53521 is rated Critical with a CVSS score of 9.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2025-53521?
Yes. A fix has been recorded for CVE-2025-53521. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2025-53521 affect?
CVE-2025-53521 affects f5:big-ip_access_policy_manager. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
- affected>= 17.5.0 and < 17.5.1.3
- affected>= 17.1.0 and < 17.1.3
- affected>= 16.1.0 and < 16.1.6.1
- affected>= 15.1.0 and < 15.1.10.8
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
cisa ssvc
- exploitation
- active
- automatable
- yes
- technical impact
- total
Assessed by CISA 28 Mar 2026 (SSVC 2.0.3).
timeline
- 15 Oct 2025Published
- 27 Mar 2026Added to CISA KEV (exploited in the wild) · 162 days (about 5 months) later
- 28 Mar 2026CISA SSVC assessment: exploitation active · 1 day later
- 30 Mar 2026CISA remediation due date (US federal agencies) · 2 days later
- 31 Mar 2026CVE record last updated · 2 days later
- 2 Nov 2026Analysed by vulneraibility.com · 216 days (about 7 months) later
sources
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.