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Big Ip Access Policy ManagerApplication · F5

CVE-2021-23035

HIGH · 7.5 CVSS v3.1 Published 2021-09-14
Fix available
A fix is available. Upgrade to after 14.1.4.4 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 14.1.x before 14.1.4.4, when an HTTP profile is configured on a virtual server, after a specific sequence of packets, chunked responses 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

A denial of service vulnerability in F5 BIG-IP 14.1.x before 14.1.4.4 allows remote attackers to crash the Traffic Management Microkernel (TMM) by sending a specific sequence of packets to a virtual server configured with an HTTP profile, triggering an issue in chunked response handling.

MitigationUpgrade BIG-IP to version 14.1.4.4 or later. As a temporary workaround, avoid using HTTP profiles on vulnerable virtual servers if chunked encoding is expected, though this significantly impacts functionality.

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:>= 14.1.0, <= 14.1.4.4
Big Ip Advanced Firewall ManagerApplication
Affected:>= 14.1.0, <= 14.1.4.4
Big Ip AnalyticsApplication
Affected:>= 14.1.0, <= 14.1.4.4
Big Ip Application Acceleration ManagerApplication
Affected:>= 14.1.0, <= 14.1.4.4
Big Ip Application Security ManagerApplication
Affected:>= 14.1.0, <= 14.1.4.4
Big Ip Domain Name SystemApplication
Affected:>= 14.1.0, <= 14.1.4.4
Big Ip Fraud Protection ServiceApplication
Affected:>= 14.1.0, <= 14.1.4.4
Big Ip Global Traffic ManagerApplication
Affected:>= 14.1.0, <= 14.1.4.4

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 version
    Run `tmsh show sys version` or `tmsh show sys hardware` to determine the installed BIG-IP version
    Affected if Version starts with 14.1.x and is lower than 14.1.4.4
  2. Identify virtual servers with HTTP profiles
    Run `tmsh list ltm virtual one-line` and look for virtual servers that reference an HTTP profile in their definition
    Affected if Any virtual server references an HTTP profile (such as http, httptraffic, or custom HTTP profiles)
  3. Confirm chunked encoding is in use
    Review the HTTP profile configuration with `tmsh list ltm profile http` and check if chunked encoding handling is enabled or expected for the application traffic
    Affected if Chunked response handling is enabled or traffic uses chunked transfer encoding
  4. Verify TMM is exposed
    Confirm the BIG-IP is processing traffic by checking `tmsh show sys tmm-info` or `tmsh show ltm virtual` to see active virtual servers
    Affected if TMM is active and processing requests for virtual servers with HTTP profiles

You are affected if your BIG-IP runs version 14.1.0 through 14.1.4.4 and you have virtual servers configured with HTTP profiles processing chunked-encoded responses.

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.

dbcve · scoped
Upgrade available Upgrade to a release after 14.1.4.4
Interim mitigation

Upgrade BIG-IP to version 14.1.4.4 or later. As a temporary workaround, avoid using HTTP profiles on vulnerable virtual servers if chunked encoding is expected, though this significantly impacts functionality.

Recommended fix High confidence

BIG-IP 14.1.4.4 or later (14.1.x branch)

  1. 1. Back up the BIG-IP configuration before performing any upgrade.
  2. 2. Download BIG-IP version 14.1.4.4 or later from the F5 Downloads page (support.f5.com).
  3. 3. Upload the ISO image to the BIG-IP device via the web interface or SCP.
  4. 4. Verify the uploaded image checksum matches the official F5 checksum.
  5. 5. Install the upgrade via the web interface (System > Software Management > ISO Image > Install) or via TMSH: 'install sys software volume <volume-name> <image-name>'.
  6. 6. Reboot the BIG-IP device to complete the installation.
  7. 7. After reboot, verify the new version is running: 'tmsh show sys version'.
  8. 8. Test that virtual servers with HTTP profiles accept chunked responses without TMM termination.
Caveat Review F5 release notes for any known issues between your current version and 14.1.4.4; upgrades within the same major.minor version typically have minimal compatibility impact

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Big Ip Access Policy Manager Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,120
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,392.

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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-2021-23035 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
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  • No spam, self-promotion, credentials, or personal data