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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 30 Mar 2026.
Big Ip Access Policy ManagerApplication · F5

CVE-2025-53521

CRITICAL · 9.8 CVSS v3.1 Published 2025-10-15
Fix available
A fix is available. Upgrade to 15.1.10.8 / 16.1.6.1 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

This is a critical vulnerability in F5 BIG-IP APM (Access Policy Manager) where specially crafted malicious traffic directed at a virtual server configured with an APM access policy can result in unauthenticated Remote Code Execution (RCE) on the affected BIG-IP device.

MitigationApply the appropriate F5 security update or patch for CVE-2025-53521 to all affected BIG-IP systems. If immediate patching is not possible, consider restricting access to virtual servers with APM access policies or implementing additional filtering at upstream devices.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Big Ip Access Policy ManagerApplication
Affected:>= 15.1.0, < 15.1.10.8>= 16.1.0, < 16.1.6.1>= 17.1.0, < 17.1.3>= 17.5.0, < 17.5.1.3

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify BIG-IP version
    Run command 'tmsh show sys version' or check via web UI under System > Software Management > Image List
    Affected if Installed version is 15.1.0 through 15.1.10.7, 16.1.0 through 16.1.6.0, 17.1.0 through 17.1.2, or 17.5.0 through 17.5.1.2
  2. Verify APM module is provisioned
    Run command 'tmsh list sys provision apm' or check via web UI under System > Provisioning. Confirm the 'level' is not 'none'
    Affected if APM module is provisioned and enabled on the BIG-IP device
  3. Identify virtual servers with APM access policies
    Run 'tmsh list ltm virtual all access-policy' to list all virtual servers and their access policy settings, or inspect via web UI under Local Traffic > Virtual Servers > [select each VS] > Access Policy
    Affected if Any virtual server has an APM access policy configured (access-policy field is not empty)

The environment is affected if the BIG-IP version falls within the affected ranges AND APM is provisioned AND at least one virtual server has an APM access policy configured, exposing it to network-based attack.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 15.1.10.8 / 16.1.6.1 / 17.1.3 or later
Fixed in 15.1.10.816.1.6.117.1.3
Interim mitigation

Apply the appropriate F5 security update or patch for CVE-2025-53521 to all affected BIG-IP systems. If immediate patching is not possible, consider restricting access to virtual servers with APM access policies or implementing additional filtering at upstream devices.

Recommended fix High confidence

15.1.10.8 (or latest 15.1.x), 16.1.6.1 (or latest 16.1.x), 17.1.3 (or latest 17.1.x), or 17.5.1.3 (or latest 17.5.x)

  1. 1. Back up the BIG-IP configuration before proceeding with any upgrade.
  2. 2. Identify the current BIG-IP APM version by running 'tmsh show sys version' or checking the web UI.
  3. 3. Based on your current major version (15.1.x, 16.1.x, 17.1.x, or 17.5.x), plan upgrade to the corresponding fixed release.
  4. 4. Download the appropriate Hotfix or Cumulative Hotfix (CHF) from F5 Downloads at https://downloads.f5.com/ or obtain via F5 customer portal.
  5. 5. Upload the ISO/ISO image to the BIG-IP system via Web UI (System > Software Management > Image List) or via tmsh: 'tmsh install sys software image <filename> volume=<volume-name>'.
  6. 6. Create a new volume for the upgrade if using volume-based installation, or install directly to existing volume.
  7. 7. Verify the installation completed successfully and reboot the system to boot from the new volume.
  8. 8. After reboot, confirm the version is now at or above the fixed release (15.1.10.8, 16.1.6.1, 17.1.3, or 17.5.1.3).
Caveat F5 upgrades may have configuration or behavioral changes; test thoroughly in staging before production deployment

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Big Ip Access Policy Manager Exploited in the wild — priority engagement
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing8.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,800
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,080.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-53521 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data