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Big Ip Access Policy ManagerApplication · F5

CVE-2021-23009

HIGH · 7.5 CVSS v3.1 Published 2021-05-10
Fix available
A fix is available. Upgrade to 15.1.3 / 16.0.1.1 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
On BIG-IP version 16.0.x before 16.0.1.1 and 15.1.x before 15.1.3, malformed HTTP/2 requests may cause an infinite loop which causes a Denial of Service for Data Plane traffic. TMM takes the configured HA action when the TMM process is aborted. There is no control plane exposure, this is a data plane issue only. 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 vulnerability in F5 BIG-IP versions 15.1.x before 15.1.3 and 16.0.x before 16.0.1.1 allows remote attackers to trigger an infinite loop in the TMM (Traffic Management Module) by sending malformed HTTP/2 requests. This causes TMM to abort and triggers a Denial of Service on the data plane. The control plane is unaffected, making this a data-plane-only DoS vulnerability.

MitigationApply the vendor patches by upgrading BIG-IP to version 16.0.1.1 or later (for 16.0.x) or 15.1.3 or later (for 15.1.x). Plan an appropriate maintenance window as the upgrade will require service interruption.

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, < 15.1.3>= 16.0.0, < 16.0.1.1
Big Ip Advanced Firewall ManagerApplication
Affected:>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.1
Big Ip Advanced Web Application FirewallApplication
Affected:>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.1
Big Ip AnalyticsApplication
Affected:>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.1
Big Ip Application Acceleration ManagerApplication
Affected:>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.1
Big Ip Application Security ManagerApplication
Affected:>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.1
Big Ip Ddos Hybrid DefenderApplication
Affected:>= 15.1.0, < 15.1.3>= 16.0.0, < 16.0.1.1
Big Ip Domain Name SystemApplication
Affected:>= 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 the installed BIG-IP version
    Run `tmsh show /sys version` on the command line or view the version in the BIG-IP Configuration utility under System > Software Management > ISO Image
    Affected if The version is 15.1.0 through 15.1.2.x, or 16.0.0 through 16.0.1.0
  2. Verify HTTP/2 profile is enabled on virtual servers
    Run `tmsh list /ltm profile http2` to list all HTTP/2 profiles, then check which virtual servers reference them using `tmsh list /ltm virtual`
    Affected if An HTTP/2 profile is configured and assigned to a virtual server that accepts traffic from untrusted sources
  3. Confirm TMM is exposed to external HTTP/2 traffic
    Review virtual server configurations and firewall policies to determine if the data plane can receive HTTP/2 requests from external networks
    Affected if Virtual servers with HTTP/2 profiles are reachable from networks outside the trusted internal zone
  4. Check for TMM crash logs
    Run `tmsh show /ltm core dumps` or inspect `/var/log/ltm` for recent TMM abort entries
    Affected if TMM has crashed or aborted recently with HTTP/2-related errors

You are affected if your BIG-IP version falls within 15.1.0 to 15.1.2.x or 16.0.0 to 16.0.1.0 AND you have HTTP/2 profiles exposed to untrusted traffic, as the malformed HTTP/2 request loop will cause TMM to abort.

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 15.1.3 / 16.0.1.1 or later
Fixed in 15.1.316.0.1.1
Interim mitigation

Apply the vendor patches by upgrading BIG-IP to version 16.0.1.1 or later (for 16.0.x) or 15.1.3 or later (for 15.1.x). Plan an appropriate maintenance window as the upgrade will require service interruption.

Fix this in Big Ip Access Policy Manager Scoped from the published advisory
  • Consultation4.0 h
  • Implementation3.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,300
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $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-2021-23009 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