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Big Ip Policy Enforcement ManagerApplication · F5

CVE-2020-5942

HIGH · 7.5 CVSS v3.1 Published 2020-11-05
Fix available
A fix is available. Upgrade to 14.1.2.8 / 15.1.1 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
In BIG-IP PEM versions 16.0.0-16.0.0.1, 15.1.0-15.1.0.5, 14.1.0-14.1.2.7, 13.1.0-13.1.3.4, 12.1.0-12.1.5.2, and 11.6.1-11.6.5.2, when processing Capabilities-Exchange-Answer (CEA) packets with certain attributes from the Policy and Charging Rules Function (PCRF) server, the Traffic Management Microkernel (TMM) may generate a core file and restart.

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

In BIG-IP PEM versions 12.1.0-12.1.5.2, 13.1.0-13.1.3.4, 14.1.0-14.1.2.7, 15.1.0-15.1.0.5, and 16.0.0-16.0.1, the Traffic Management Microkernel (TMM) crashes and restarts when processing malformed Capabilities-Exchange-Answer (CEA) packets with certain attributes from the Policy and Charging Rules Function (PCRF) server. This results in a denial-of-service condition.

MitigationApply the appropriate F5 hotfix or upgrade to a fixed version of BIG-IP PEM as specified in the F5 security advisory. Implement network segmentation to restrict PCRF server communications to trusted sources.

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 Policy Enforcement ManagerApplication
Affected:>= 11.6.1, <= 11.6.5.2>= 12.1.0, <= 12.1.5.2>= 13.1.0, <= 13.1.3.4>= 14.1.0, < 14.1.2.8>= 15.1.0, < 15.1.1>= 16.0.0, < 16.0.1

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. Verify BIG-IP PEM module is installed
    Run 'tmsh show sys module' or check the F5 management console for Policy Enforcement Manager module status
    Affected if PEM module is not present or not provisioned (the vulnerability only applies if PEM is installed)
  2. Determine installed PEM version
    Run 'tmsh show sys version' or check 'tmsh list sys module version' for the PEM module version number
    Affected if The version falls within these ranges: 11.6.1-11.6.5.2, 12.1.0-12.1.5.2, 13.1.0-13.1.3.4, 14.1.0-14.1.2.7, 15.1.0-15.1.0.5, or 16.0.0-16.0.0 (any version before the fixed releases)
  3. Confirm PCRF server communication is configured
    Run 'tmsh list pem node' and 'tmsh list pem server' to check for PCRF server entries, or review the PEM configuration for active PCRF connections
    Affected if PCRF server entries exist in the configuration - the vulnerability is triggered by malformed CEA packets from the PCRF server, so active PCRF communication is required for exploitation
  4. Review TMM crash logs for related events
    Check '/var/log/ltm' for TMM crash indicators or run 'tmsh show tmm crash' to see recent crash history
    Affected if TMM crashes or restarts are logged with PCRF/CEA-related messages, indicating potential exploitation attempts

The environment is affected if BIG-IP PEM is installed with a version in the affected ranges AND PCRF server communication is configured, as the vulnerability requires malformed CEA packets from a PCRF server to trigger the TMM crash.

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 14.1.2.8 / 15.1.1 / 16.0.1 or later
Fixed in 14.1.2.815.1.116.0.1
Interim mitigation

Apply the appropriate F5 hotfix or upgrade to a fixed version of BIG-IP PEM as specified in the F5 security advisory. Implement network segmentation to restrict PCRF server communications to trusted sources.

Fix this in Big Ip Policy Enforcement Manager Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,330
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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-2020-5942 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