CVE-2025-53521
Exploitation confirmed. First attested on 2026-03-27 by CISA-ADP, CISA KEV, GCVE · kevintel.
- Published2025-10-15
- Fixed in17.5.1.3 · 17.1.3 · 16.1.6.1 · 15.1.10.8
- WeaknessCWE-121
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « affected ».With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.
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.
Timeline
dates in UTCObserved activity
isMalicious corpus · updated 2026-10-23 18:48 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2025-53521?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2025-53521?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
NVD| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 17.5 | ≥ 17.5.0, < 17.5.1.3 | 17.5.1.3 | NVD |
| 17.1 | ≥ 17.1.0, < 17.1.3 | 17.1.3 | NVD |
| 16.1 | ≥ 16.1.0, < 16.1.6.1 | 16.1.6.1 | NVD |
| 15.1 | ≥ 15.1.0, < 15.1.10.8 | 15.1.10.8 | NVD |
as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.
Fix
- Update F5 big-ip access policy manager to 17.5.1.3 · 17.1.3 · 16.1.6.1 · 15.1.10.8
- CISA’s 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 2026-03-30
Advisories and patches
- my.f5.comVendor Advisory
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
CISA Known Exploited Vulnerability
- Date Added
- 2026-03-27
- Patch Due Date
- 2026-03-30
- Ransomware Use
- Unknown
- 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.
Sources
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CVSS 4.0 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
- Published
- 2025-10-15
- Last Modified
- 2026-10-08
- NVD status
- Analyzed
- CERT-FR Advisory
- CERTFR-2026-ALE-004
- CERT-FR Link
- CERTFR-2026-ALE-004
Frequently asked questions
What is CVE-2025-53521?
Is CVE-2025-53521 actively exploited?
What is the CVSS score for CVE-2025-53521?
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Surveillance reads the versions in your stack — a domain, a lockfile or a list — checks each CVE against the ranges its sources publish, and alerts you when one you run is exploited or enters CISA KEV. A version it cannot read stays « version not verified ».
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Related vulnerabilities
Same product first, then the same vendor advisory and the same publication week.