Big Ip Advanced Web Application FirewallApplication · F5
CVE-2020-27718
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 a BIG-IP ASM or Advanced WAF system running version 16.0.0-16.0.0.1, 15.1.0-15.1.0.5, 14.1.0-14.1.3, 13.1.0-13.1.3.4, 12.1.0-12.1.5.2, or 11.6.1-11.6.5.2 processes requests with JSON payload, 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 confidenceThis is a denial-of-service vulnerability in F5 BIG-IP ASM/Advanced WAF where specially crafted HTTP requests containing JSON payloads with an unusually large number of parameters cause excessive CPU consumption in the ASM bd (background daemon) process, potentially rendering the system unresponsive.
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
>= 11.6.1, <= 11.6.5>= 12.1.0, <= 12.1.5>= 13.1.0, < 13.1.3.5>= 14.1.0, < 14.1.3.1>= 15.0.0, < 15.1.1>= 16.0.0, < 16.0.1
Big Ip Application Security ManagerApplication
>= 11.6.1, <= 11.6.5>= 12.1.0, <= 12.1.5>= 13.1.0, < 13.1.3.5>= 14.1.0, < 14.1.3.1>= 15.0.0, < 15.1.1>= 16.0.0, < 16.0.1CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Identify BIG-IP versionRun command: tmsh show /sys version or check /etc/product_versionAffected if The installed version falls within 11.6.1-11.6.5, 12.1.0-12.1.5, 13.1.0-13.1.4, 14.1.0-14.1.3, 15.0.0-15.1.1, or 16.0.0-16.0.1
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Verify ASM or Advanced WAF module is provisionedRun command: tmsh show /sys provision and look for asm or advanced-waf module statusAffected if asm or advanced-waf shows as provisioned (not none)
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Confirm ASM security policy is activeRun command: tmsh list /asm policy or check via web UI under Security > Application Security > PoliciesAffected if An ASM policy exists and is enforced on a virtual server
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Check if system accepts JSON API trafficReview virtual server configurations: tmsh list /ltm virtual all and inspect whether JSON content types are allowed in the ASM policy parsing settingsAffected if The ASM policy accepts JSON payload requests (Content-Type: application/json) and does not have parameter count limits configured
The environment is affected if BIG-IP runs a vulnerable version listed above, ASM or Advanced WAF is provisioned and actively enforcing a policy that accepts JSON payloads without parameter count restrictions.
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 data13.1.3.514.1.3.115.1.1
Upgrade BIG-IP to a patched version beyond those listed as affected, or implement rate limiting on JSON API endpoints to restrict the number of parameters accepted per request.
Fix this in Big Ip Advanced Web Application Firewall
Scoped from the published advisory
- Consultation3.0 h
- Implementation6.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-27718 — 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-2020-27718 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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