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Big Ip Access Policy ManagerApplication · F5

CVE-2021-23011

HIGH · 7.5 CVSS v3.1 Published 2021-05-10
Fix available
A fix is available. Upgrade to 11.6.5.3 / 12.1.6 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
On versions 16.0.x before 16.0.1.1, 15.1.x before 15.1.3, 14.1.x before 14.1.4, 13.1.x before 13.1.4, 12.1.x before 12.1.6, and 11.6.x before 11.6.5.3, when the BIG-IP system is buffering packet fragments for reassembly, the Traffic Management Microkernel (TMM) may consume an excessive amount of resources, eventually leading to a restart and failover event. 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 · high confidence

This is a denial-of-service vulnerability in F5 BIG-IP's Traffic Management Microkernel (TMM). When the system buffers packet fragments for reassembly, an attacker can send specially crafted fragmented packets to exhaust TMM resources, causing the system to restart and trigger failover. The vulnerability is exploitable remotely without authentication and affects multiple version branches across the BIG-IP product line.

MitigationApply the appropriate patched version for each affected branch: 16.0.1.1 or later, 15.1.3 or later, 14.1.4 or later, 13.1.4 or later, 12.1.6 or later, or 11.6.5.3 or later. Schedule the update during a maintenance window and verify failover functionality after patching.

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:>= 11.6.1, < 11.6.5.3>= 12.1.0, < 12.1.6>= 13.1.0, < 13.1.4>= 14.1.0, < 14.1.4>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.1
Big Ip Advanced Firewall ManagerApplication
Affected:>= 11.6.1, < 11.6.5.3>= 12.1.0, < 12.1.6>= 13.1.0, < 13.1.4>= 14.1.0, < 14.1.4>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.1
Big Ip Advanced Web Application FirewallApplication
Affected:>= 11.6.1, < 11.6.5.3>= 12.1.0, < 12.1.6>= 13.1.0, < 13.1.4>= 14.1.0, < 14.1.4>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.1
Big Ip AnalyticsApplication
Affected:>= 11.6.1, < 11.6.5.3>= 12.1.0, < 12.1.6>= 13.1.0, < 13.1.4>= 14.1.0, < 14.1.4>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.1
Big Ip Application Acceleration ManagerApplication
Affected:>= 11.6.1, < 11.6.5.3>= 12.1.0, < 12.1.6>= 13.1.0, < 13.1.4>= 14.1.0, < 14.1.4>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.1
Big Ip Application Security ManagerApplication
Affected:>= 11.6.1, < 11.6.5.3>= 12.1.0, < 12.1.6>= 13.1.0, < 13.1.4>= 14.1.0, < 14.1.4>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.1
Big Ip Ddos Hybrid DefenderApplication
Affected:>= 11.6.1, < 11.6.5.3>= 12.1.0, < 12.1.6>= 13.1.0, < 13.1.4>= 14.1.0, < 14.1.4>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.1
Big Ip Domain Name SystemApplication
Affected:>= 11.6.1, < 11.6.5.3>= 12.1.0, < 12.1.6>= 13.1.0, < 13.1.4>= 14.1.0, < 14.1.4>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.1

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. Check BIG-IP system version
    Run 'tmsh show sys version' or view /etc/product_version on the BIG-IP device
    Affected if Version is 11.6.1 to 11.6.5.2, 12.1.0 to 12.1.5, 13.1.0 to 13.1.3, 14.1.0 to 14.1.3, 15.1.0 to 15.1.2, or 16.0.0 to 16.0.1.0 (any version below the fixed releases)
  2. Identify installed BIG-IP modules
    Run 'tmsh list sys provision' to see which modules are provisioned on the system
    Affected if Any of these modules are provisioned: apm, afm, analytics, aam, asm, dos (ddos hybrid defender), or gtm/dns
  3. Confirm TMM is active
    Verify the Traffic Management Microkernel is running via 'tmsh show sys tmm' or 'tmsh show sys mcp-state'
    Affected if TMM is running (this is the default operational state for BIG-IP)
  4. Verify packet processing is enabled
    Check that network traffic processing is active - this is inherent to TMM operation by default
    Affected if The system is accepting and processing network traffic, which enables the fragment reassembly path

The environment is affected if the BIG-IP version falls within the vulnerable ranges and any of the BIG-IP modules (APM, AFM, AWF, Analytics, AAM, ASM, DDoS Hybrid Defender, or DNS) are provisioned, since TMM processes packets by default.

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 11.6.5.3 / 12.1.6 / 13.1.4 or later
Fixed in 11.6.5.312.1.613.1.4
Interim mitigation

Apply the appropriate patched version for each affected branch: 16.0.1.1 or later, 15.1.3 or later, 14.1.4 or later, 13.1.4 or later, 12.1.6 or later, or 11.6.5.3 or later. Schedule the update during a maintenance window and verify failover functionality after patching.

Fix this in Big Ip Access Policy Manager Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing3.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,570
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,512.

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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-2021-23011 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
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  • Version or environment caveats, and links to real fixes
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