Buffer overflow in F5 Big-Ip
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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.023 (83.0th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 83rd percentile — 83.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.023 · newest: 0.023 · change: 0.000
Affected products
- F5 Big-Ip — versions 17.5.0, 17.1.0, 16.1.0
- F5 Big-Ip Access Policy Manager
Weakness classification (CWE)
CISA KEV (Known Exploited Vulnerabilities)
This CVE is on the CISA KEV catalog, added on . CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.
BOD 22-01 due date: .
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.
References
- my.f5.com/manage/s/article/K000156741 (vendor-advisory, Vendor Advisory)
- 134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)
Frequently asked questions
- What is CVE-2025-53521?
- CVE-2025-53521 is a critical-severity vulnerability in F5 Big-Ip, classified under Stack-based Buffer Overflow. CVSS score: 9.8/10. Published 2025-10-15.
- How severe is CVE-2025-53521?
- Critical severity. CVSS v3 base score is 9.8 out of 10.
- Is CVE-2025-53521 known to be exploited?
- Yes. CVE-2025-53521 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-03-27), indicating it is being actively exploited.