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Big Ip Access Policy ManagerApplication · F5

CVE-2026-41218

HIGH · 7.5 CVSS v3.1 Published 2026-05-13
Fix available
A fix is available. Upgrade to after 17.5.1 or later.
See remediation →
84/100
Remediation priority · High
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 BIG-IP PEM iRules are configured on a virtual server (iRules using commands starting with CLASSIFICATION::, CLASSIFY::, PEM::, PSC::, and the urlcatquery command), undisclosed traffic can cause the Traffic Management Microkernel (TMM) to terminate.  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 denial-of-service vulnerability in BIG-IP PEM (Policy Enforcement Manager) iRules. When the Traffic Management Microkernel (TMM) processes undisclosed traffic patterns through virtual servers configured with specific iRule commands (CLASSIFICATION::, CLASSIFY::, PEM::, PSC::, or urlcatquery), it causes TMM to terminate unexpectedly, disrupting all traffic through affected virtual servers.

MitigationRemove or disable the vulnerable PEM iRules from affected virtual servers until an official F5 patch is available. If immediate removal is not feasible, consider restricting access to the virtual servers or implementing upstream filtering as a temporary compensating control.

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:>= 17.1.0, <= 17.1.3>= 17.5.0, <= 17.5.1>= 16.1.0, <= 16.1.6= 21.0.0
Big Ip Advanced Firewall ManagerApplication
Affected:>= 17.1.0, <= 17.1.3>= 17.5.0, <= 17.5.1>= 16.1.0, <= 16.1.6= 21.0.0
Big Ip Advanced Web Application FirewallApplication
Affected:>= 17.1.0, <= 17.1.3>= 17.5.0, <= 17.5.1>= 16.1.0, <= 16.1.6= 21.0.0
Big Ip AnalyticsApplication
Affected:>= 17.1.0, <= 17.1.3>= 17.5.0, <= 17.5.1>= 16.1.0, <= 16.1.6= 21.0.0
Big Ip Application Acceleration ManagerApplication
Affected:>= 17.1.0, <= 17.1.3>= 17.5.0, <= 17.5.1>= 16.1.0, <= 16.1.6= 21.0.0
Big Ip Application Security ManagerApplication
Affected:>= 17.1.0, <= 17.1.3>= 17.5.0, <= 17.5.1>= 16.1.0, <= 16.1.6= 21.0.0
Big Ip Application Visibility And ReportingApplication
Affected:>= 17.1.0, <= 17.1.3>= 17.5.0, <= 17.5.1>= 16.1.0, <= 16.1.6= 21.0.0
Big Ip Automation ToolchainApplication
Affected:>= 17.1.0, <= 17.1.3>= 17.5.0, <= 17.5.1>= 16.1.0, <= 16.1.6= 21.0.0

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
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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. Check BIG-IP system version
    Run `tmsh show sys version` or view System > Software Management > Image List in the GUI. Identify the installed BIG-IP version number.
    Affected if Version matches 17.1.0-17.1.3, 17.5.0-17.5.1, 16.1.0-16.1.6, or 21.0.0
  2. List all configured iRules
    Run `tmsh list ltm rule all` to retrieve all iRules defined on the system.
    Affected if Any iRule contains CLASSIFICATION::, CLASSIFY::, PEM::, PSC::, or urlcatquery commands
  3. Identify virtual servers using vulnerable iRules
    Run `tmsh list ltm virtual all` and cross-reference with the iRules from step 2. Alternatively, for each suspect iRule run `tmsh list ltm rule <rule_name>` to see which virtual servers reference it.
    Affected if A virtual server references an iRule containing the vulnerable commands and that virtual server is active
  4. Confirm TMM restart events
    Check TMM crash logs at /var/log/ltm for unexpected TMM termination events, or run `tmsh show ltm core` to list any core dump files.
    Affected if TMM has restarted or core dumps exist on systems with vulnerable iRule configurations

Environment is affected if the BIG-IP version falls within the listed ranges AND virtual servers are configured with iRules containing CLASSIFICATION::, CLASSIFY::, PEM::, PSC::, or urlcatquery commands.

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.

From vendor data
Upgrade available Upgrade to a release after 17.5.1
Interim mitigation

Remove or disable the vulnerable PEM iRules from affected virtual servers until an official F5 patch is available. If immediate removal is not feasible, consider restricting access to the virtual servers or implementing upstream filtering as a temporary compensating control.

Fix this in Big Ip Access Policy Manager Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA3.0 h
21.0 hours of engineering $3,680
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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-2026-41218 in production — separate from our analysis above.

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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