What it is
CVE-2025-53521 is an unauthenticated BigIP APM Vulnerability affecting 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...
Vulnerability report
Exploited in the wild
Confirmed confidence
In CISA KEV
CVE-2025-53521
BigIP APM Vulnerability
F5 / BIG-IP · affected before 17.5.1.3
- Severity
- CVSS 9.3 · Critical
- Confidence
- Confirmed
- Exploit status
- Exploited in the wild
- EPSS
- 2.2%
- First observed
- —
- Last observed
- —
Decision summary
What security teams need to know first
Direct answers before the deeper technical record.
Is it exploited?
Yes. KEV Intelligence tracks this CVE as a known exploited vulnerability. Confidence is confirmed.
Who is affected?
F5 / BIG-IP affected before 17.5.1.3.
What should we do?
Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
Overview
BigIP APM Vulnerability
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.
Vendor
Product
Affected
Status
F5
BIG-IP
Before 17.5.1.3
Affected
F5
BIG-IP
Before 17.1.3
Affected
F5
BIG-IP
Before 16.1.6.1
Affected
F5
BIG-IP
Before 15.1.10.8
Affected
- Published
- 15 Oct 2025
- Exploitation Reported
- 01 Jun 2026
- Attack vector
- Remote
- Complexity
- Low
- Privileges
- None
- User interaction
- None
Tags
cisa
edge
CVE References
- CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2025-53521
- Vendor Advisory — my.f5.com my.f5.com · Vendor Advisory https://my.f5.com/manage/s/article/K000156741
Exploitation evidence
Why KEV Intelligence marks this CVE as exploited
Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.
Exploited in the wild
CVE
Independent exploitation attestation added to the KEV Intelligence record.
Known exploited vulnerability sources
Per-source evidence links for KEV attestations are available through the KEV Intelligence Pro API.
Learn about Pro API access| Source | Added |
|---|---|
| CVE First | 2026-06-01 12:26 UTC |
| CISA | 2026-06-02 14:02 UTC |
Detection
Operational artifacts and observed signals
Make the evidence actionable in scanner, SOC, and edge-control workflows.
Observed signals
- Request targets
- 0
- User-Agents
- 0
Raw values available in Pro and Enterprise.
Scanner coverage
No scanner integrations recorded yet.
Virtual patch status
No KEV Intelligence virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.
Learn about virtual patches →No detection artifacts or sensor request patterns are available for this CVE yet.
Check back as sensor telemetry and scanner integrations are updated.
Risk and context
Severity, weaknesses, and research context
CVSS v4.0
9.3
Critical
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
EPSS
2.2%
Weaknesses
All CVSS Scores
CVSS v4.0
9.3
Critical
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
CVSS v3.1
9.8
Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Timeline
From disclosure to observed exploitation
-
Added to CISA KEV
Listed in the CISA Known Exploited Vulnerabilities catalog
-
Added to KEV Intelligence KEV Feed
High-confidence, third-party attested exploitation
-
CVE published
Vulnerability disclosed publicly
-
CVE ID reserved
Identifier reserved by the CNA
Pro API
Automate this intelligence
Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.
- Evidence confidence and provenance
- First-party sensor telemetry
- PoC and scanner references
- Affected versions and enrichment
- Automation-ready JSON delivery
GET /api/v2/pro/kevs/CVE-2025-53521
Free JSON includes basic KEV fields{
"cve_id": "CVE-2025-53521",
"confidence": "Confirmed",
"cvss_score": 9.3,
"cvss_estimated": false,
"epss_score": 0.02213,
"exploit_status": {
"exploited_in_the_wild": true,
"active_exploitation_observed": false
},
"sensor_telemetry": { "attempts": 0, "sensors": 0 }
}Early warning alerts
Get alerts on high-impact exploitation
Receive curator-selected alerts when exploitation activity warrants attention. Each alert includes the evidence and context needed to decide what requires attention now.