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Big Ip Advanced Web Application FirewallApplication · F5

CVE-2021-23033

HIGH · 7.5 CVSS v3.1 Published 2021-09-14
Fix available
A fix is available. Upgrade to 13.1.4.1 / 14.1.4.3 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 Advanced WAF and BIG-IP ASM version 16.x before 16.1.0x, 15.1.x before 15.1.3.1, 14.1.x before 14.1.4.3, 13.1.x before 13.1.4.1, and all versions of 12.1.x, when a WebSocket profile is configured on a virtual server, undisclosed requests can cause bd 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 · high confidence

A denial of service vulnerability in F5 BIG-IP Advanced WAF and ASM allows unauthenticated attackers to crash the bigd daemon by sending specially crafted requests through virtual servers with WebSocket profiles enabled. The vulnerability affects multiple version branches (16.x before 16.1.0, 15.1.x before 15.1.3.1, 14.1.x before 14.1.4.3, 13.1.x before 13.1.4.1, and all 12.1.x versions).

MitigationUpgrade BIG-IP to the patched version (16.1.0+, 15.1.3.1+, 14.1.4.3+, or 13.1.4.1+) as the primary remediation. If immediate patching is not feasible, consider disabling or removing WebSocket profiles on affected virtual servers as a temporary workaround.

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 Advanced Web Application FirewallApplication
Affected:>= 12.1.0, <= 12.1.6>= 13.1.0, < 13.1.4.1>= 14.1.0, < 14.1.4.3>= 15.1.0, < 15.1.3.1>= 16.0.0, < 16.1.0
Big Ip Application Security ManagerApplication
Affected:>= 12.1.0, <= 12.1.6>= 13.1.0, < 13.1.4.1>= 14.1.0, < 14.1.4.3>= 15.1.0, < 15.1.3.1>= 16.0.0, < 16.1.0

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. Confirm BIG-IP module is Advanced WAF or ASM
    Run 'tmsh show sys license' or check the GUI under System > License to verify the licensed module includes Advanced WAF or Application Security Manager.
    Affected if The module is Advanced WAF or ASM and the version falls within the affected ranges.
  2. Determine the installed BIG-IP version
    Run 'tmsh show sys version' or check the BIG-IP version from the GUI (Main tab > Overview > Summary). Compare the version number to the affected ranges: 12.1.0-12.1.6, 13.1.0-13.1.4.0, 14.1.0-14.1.4.2, 15.1.0-15.1.3.0, or 16.0.0-16.0.x.
    Affected if The installed version is within any of these ranges.
  3. Identify virtual servers with WebSocket profiles
    Run 'tmsh list ltm virtual one-line' to list all virtual servers, then run 'tmsh list ltm profile websocket' to list all WebSocket profiles. Cross-reference to identify virtual servers referencing a WebSocket profile.
    Affected if Any virtual server has a WebSocket profile assigned.
  4. Verify WebSocket profile is enabled on affected virtual servers
    For each virtual server with a WebSocket profile, run 'tmsh list ltm virtual <name>' and inspect the 'websocket-profile' setting to confirm it is enabled.
    Affected if A WebSocket profile is explicitly assigned and enabled on a virtual server.

The environment is affected if BIG-IP runs Advanced WAF or ASM, the version falls within the vulnerable ranges, AND any virtual server has a WebSocket profile enabled.

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 13.1.4.1 / 14.1.4.3 / 15.1.3.1 or later
Fixed in 13.1.4.114.1.4.315.1.3.1
Interim mitigation

Upgrade BIG-IP to the patched version (16.1.0+, 15.1.3.1+, 14.1.4.3+, or 13.1.4.1+) as the primary remediation. If immediate patching is not feasible, consider disabling or removing WebSocket profiles on affected virtual servers as a temporary workaround.

Recommended fix High confidence

Upgrade to 13.1.4.1 (or later 13.1.x), 14.1.4.3 (or later 14.1.x), or 15.1.3.1 (or later 15.1.x) depending on your current branch; 12.1.x users should upgrade to a currently supported branch

  1. 1. Identify the currently deployed BIG-IP Advanced WAF or BIG-IP ASM version using 'tmsh show sys version' or the web management console.
  2. 2. Determine which version branch (12.1.x, 13.1.x, 14.1.x, or 15.1.x) is currently in use.
  3. 3. For 12.1.x versions: Note that this branch has reached End of Technical Support (EoTS) and F5 recommends upgrading to a actively supported version branch.
  4. 4. For 13.1.x versions: Upgrade to version 13.1.4.1 or later.
  5. 5. For 14.1.x versions: Upgrade to version 14.1.4.3 or later.
  6. 6. For 15.1.x versions: Upgrade to version 15.1.3.1 or later.
  7. 7. Download the target version from the F5 downloads portal (downloads.f5.com) or retrieve from F5 licensing portal.
  8. 8. Review F5 release notes for the target version to verify compatibility with your deployment.
Caveat Review F5 release notes for known issues - some upgrades may require careful planning due to configuration changes between major.minor versions

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

Fix this in Big Ip Advanced Web Application Firewall Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2021-23033 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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