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Big Ip Access Policy ManagerApplication · F5

CVE-2020-5921

HIGH · 7.5 CVSS v3.1 Published 2020-08-26
Fix available
A fix is available. Upgrade to 12.1.5.2 / 14.1.2.7 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 versions 15.1.0-15.1.0.4, 15.0.0-15.0.1.3, 14.1.0-14.1.2.6, 13.1.0-13.1.3.4, 12.1.0-12.1.5.1, and 11.6.1-11.6.5.2, Syn flood causes large number of MCPD context messages destined to secondary blades consuming memory leading to MCPD failure. This issue affects only VIPRION hosts with two or more blades installed. Single-blade VIPRION hosts are not affected.

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 · high confidence

A SYN flood attack on BIG-IP VIPRION systems with two or more blades triggers excessive MCPD (Management Configuration Daemon) context messages between the blades, consuming memory and potentially causing MCPD failure, resulting in denial of service.

MitigationApply the appropriate F5 hotfix for the affected BIG-IP version or upgrade to a patched release. This vulnerability only affects VIPRION chassis with multiple blades; single-blade VIPRION and non-VIPRION systems are not affected.

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:>= 12.1.0, < 12.1.5.2>= 14.1.0, < 14.1.2.7>= 15.0.0, < 15.0.1.4>= 15.1.0, < 15.1.0.5
Big Ip Advanced Firewall ManagerApplication
Affected:>= 12.1.0, < 12.1.5.2>= 14.1.0, < 14.1.2.7>= 15.0.0, < 15.0.1.4>= 15.1.0, < 15.1.0.5
Big Ip AnalyticsApplication
Affected:>= 12.1.0, < 12.1.5.2>= 14.1.0, < 14.1.2.7>= 15.0.0, < 15.0.1.4>= 15.1.0, < 15.1.0.5
Big Ip Application Acceleration ManagerApplication
Affected:>= 12.1.0, < 12.1.5.2>= 14.1.0, < 14.1.2.7>= 15.0.0, < 15.0.1.4>= 15.1.0, < 15.1.0.5
Big Ip Application Security ManagerApplication
Affected:>= 12.1.0, < 12.1.5.2>= 14.1.0, < 14.1.2.7>= 15.0.0, < 15.0.1.4>= 15.1.0, < 15.1.0.5
Big Ip Domain Name SystemApplication
Affected:>= 12.1.0, < 12.1.5.2>= 14.1.0, < 14.1.2.7>= 15.0.0, < 15.0.1.4>= 15.1.0, < 15.1.0.5
Big Ip Fraud Protection ServiceApplication
Affected:>= 12.1.0, < 12.1.5.2>= 14.1.0, < 14.1.2.7>= 15.0.0, < 15.0.1.4>= 15.1.0, < 15.1.0.5
Big Ip Global Traffic ManagerApplication
Affected:>= 12.1.0, < 12.1.5.2>= 14.1.0, < 14.1.2.7>= 15.0.0, < 15.0.1.4>= 15.1.0, < 15.1.0.5

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. Identify BIG-IP product and version
    Run `tmsh show /sys version` or `show sys version` to display the installed software version and module information
    Affected if The version falls within >= 12.1.0, < 12.1.5.2 OR >= 14.1.0, < 14.1.2.7 OR >= 15.0.0, < 15.0.1.4 OR >= 15.1.0, < 15.1.0.5
  2. Verify hardware platform is VIPRION
    Run `tmsh show /sys hardware` or `show sys hardware` to display the system hardware platform information
    Affected if The hardware platform shows VIPRION chassis (not a standalone BIG-IP or single-blade VIPRION)
  3. Count installed blades in VIPRION chassis
    Check the blade count in the hardware output from the previous step or run `tmsh show /sys blade` to list all blades
    Affected if The system has two or more blades installed and active in the VIPRION chassis
  4. Monitor MCPD memory consumption
    Run `tmsh show /ltm virtual` to observe virtual server status and check system logs for MCPD-related errors using `tmsh show /sys log mcpd`
    Affected if MCPD is consuming excessive memory, experiencing restarts, or generating error messages about context message flooding

You are affected if you are running a vulnerable BIG-IP version on a VIPRION chassis with two or more blades receiving SYN flood traffic that triggers excessive MCPD messaging between blades.

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 12.1.5.2 / 14.1.2.7 / 15.0.1.4 or later
Fixed in 12.1.5.214.1.2.715.0.1.4
Interim mitigation

Apply the appropriate F5 hotfix for the affected BIG-IP version or upgrade to a patched release. This vulnerability only affects VIPRION chassis with multiple blades; single-blade VIPRION and non-VIPRION systems are not affected.

Fix this in Big Ip Access Policy Manager Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
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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-2020-5921 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