Big Ip Application Security ManagerApplication · F5
CVE-2018-5541
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 · uneditedWhen F5 BIG-IP ASM 13.0.0-13.1.0.1, 12.1.0-12.1.3.5, 11.6.0-11.6.3.1, or 11.5.1-11.5.6 is processing HTTP requests, an unusually large number of parameters can cause excessive CPU usage in the BIG-IP ASM bd process.
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 confidenceF5 BIG-IP ASM versions 11.5.1-11.6.3.1 and 12.1.0-13.1.0.1 contain a denial-of-service vulnerability in the ASM bd (buffer director) process. When the ASM module processes HTTP requests containing an unusually large number of parameters, it causes excessive CPU consumption in the bd process, potentially leading to service degradation or unavailability.
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 Application Security ManagerApplication
>= 11.5.1, <= 11.5.5>= 11.6.1, <= 11.6.3>= 12.1.0, <= 12.1.3>= 13.0.0, <= 13.1.0CVSS 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:3.0/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 checksWork through these to decide whether this CVE applies to you.
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Identify installed BIG-IP ASM versionRun 'tmsh show sys module' or check the BIG-IP version via the web UI (System > Software Management > Image List) or command line: 'tmsh show sys version'Affected if The version falls within 11.5.1-11.6.3.1 or 12.1.0-13.1.0.1 (specifically 11.5.1-11.5.5, 11.6.1-11.6.3, 12.1.0-12.1.3, or 13.0.0-13.1.0)
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Verify ASM module is provisionedRun 'tmsh show sys provision' or check via the web UI (System > Provisioning) to confirm ASM module statusAffected if ASM is provisioned and running (the vulnerability only affects systems with ASM enabled)
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Monitor bd process CPU consumptionRun 'top -b -n 1 | grep bd' or use 'tmsh show sys process' to identify the bd process and observe CPU usageAffected if The bd process shows unusually high or sustained CPU consumption, especially when processing HTTP traffic
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Review ASM policy parameter limitsAccess ASM policy via web UI (Security > Application Security > Parameters) or run 'tmsh list asm policy' to inspect configured parameter limitsAffected if No parameter count limits are configured in the ASM policy, allowing unlimited parameters per request
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Inspect HTTP traffic for parameter-heavy requestsAnalyze logs via 'tmsh show ltm log' or capture traffic with tcpdump to identify requests with abnormally high parameter countsAffected if Incoming HTTP requests contain unusually large numbers of parameters (dozens to hundreds)
You are affected if your BIG-IP runs a vulnerable ASM version (11.5.1-13.1.0.1) with ASM provisioned, and you observe high bd process CPU or accept requests with excessive parameters.
Generated from the published advisory. Verify against your own configuration.
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 dataApply the appropriate F5 hotfix or upgrade to a fixed version as specified in F5 K23532467. As a temporary workaround, consider implementing rate limiting or request size restrictions on the ASM policy to limit the number of parameters accepted per request.
Fix this in Big Ip Application Security Manager
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-5541 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2018-5541 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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