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

Watch CVE-2025-53521 Browse KEV feed
Severity
CVSS 9.3 · Critical
Confidence
Confirmed
Exploit status
Exploited in the wild
EPSS
2.3%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

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...

Is it exploited?

Yes. Previdian tracks this CVE as a known exploited vulnerability. Confidence is confirmed. Listed in CISA KEV. Also confirmed by third-party sources.

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.

F5 Affected
BIG-IP
Before 17.5.1.3 Before 17.1.3 Before 16.1.6.1 Before 15.1.10.8
View vendor advisory (opens in new tab)
Published
15 Oct 2025
Exploitation Reported
01 Jun 2026
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

cisa edge

CVE References

Exploitation evidence

Why Previdian 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

Recorded 01 Jun 2026

A trusted third party reported exploitation.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

Learn about Pro API access
Source Added
CVE First 2026-06-01 12:26 UTC
CISA 2026-06-02 14:02 UTC
The Hacker News 2026-09-23 08:31 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
0
0
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Scanner coverage

No scanner integrations recorded yet.

Virtual patch status

No Previdian 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

Potential damage if exploited. Separate from whether attackers are using it.

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

2.3%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Stack-based Buffer Overflow CWE-121

Recent mention · The Hacker News

F5 Patches Critical BIG-IP APM Zero-Day Exploited for Unauthenticated RCE on OAuth Servers

Swati KhandelwalSep 23, 2026Vulnerability / Network Security Attackers are exploiting a critical flaw in F5 BIG-IP Access Policy Manager (APM) that lets them run code on a BIG-IP system without logging in, F5 says. The flaw, CVE-2026-94127, affects only systems in which APM...

Read full advisory

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

  1. 08:31 UTC

    KEV confirmed by The Hacker News

    Exploitation attested by an external source

  2. 14:02 UTC

    Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  3. 12:26 UTC

    Added to Previdian KEV Feed

    High-confidence, third-party attested exploitation

  4. 13:55 UTC

    CVE published

    Vulnerability disclosed publicly

  5. 23:04 UTC

    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.

Start 14-day Pro trial Read API docs
  • 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

Sample API response 
{
  "cve_id": "CVE-2025-53521",
  "confidence": "Confirmed",
  "cvss_score": 9.3,
  "cvss_estimated": false,
  "epss_score": 0.02295,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}