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Big Ip Access Policy ManagerApplication · F5

CVE-2020-5891

HIGH · 7.5 CVSS v3.1 Published 2020-04-30
Fix available
A fix is available. Upgrade to after 15.1.0.1 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 15.1.0-15.1.0.1, 15.0.0-15.0.1.2, and 14.1.0-14.1.2.3, undisclosed HTTP/2 requests can lead to a denial of service when sent to a virtual server configured with the Fallback Host setting and a server-side HTTP/2 profile.

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 is a denial of service vulnerability in F5 BIG-IP where specially crafted HTTP/2 requests sent to a virtual server configured with both a Fallback Host setting and a server-side HTTP/2 profile can cause the service to become unavailable. The vulnerability stems from improper handling of certain HTTP/2 request patterns in the affected configurations.

MitigationUpgrade BIG-IP to a version beyond the affected releases (15.1.0.2+, 15.0.1.3+, 14.1.2.4+) or apply the available hotfix. Alternatively, if immediate patching is not feasible, consider removing the Fallback Host configuration from affected virtual servers as a temporary workaround while planning the upgrade.

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, <= 14.1.2.3>= 15.0.0, <= 15.0.1.2>= 15.1.0, <= 15.1.0.1
Big Ip Advanced Firewall ManagerApplication
Affected:>= 14.1.0, <= 14.1.2.3>= 15.0.0, <= 15.0.1.2>= 15.1.0, <= 15.1.0.1
Big Ip AnalyticsApplication
Affected:>= 14.1.0, <= 14.1.2.3>= 15.0.0, <= 15.0.1.2>= 15.1.0, <= 15.1.0.1
Big Ip Application Acceleration ManagerApplication
Affected:>= 14.1.0, <= 14.1.2.3>= 15.0.0, <= 15.0.1.2>= 15.1.0, <= 15.1.0.1
Big Ip Application Security ManagerApplication
Affected:>= 14.1.0, <= 14.1.2.3>= 15.0.0, <= 15.0.1.2>= 15.1.0, <= 15.1.0.1
Big Ip Fraud Protection ServiceApplication
Affected:>= 14.1.0, <= 14.1.2.3>= 15.0.0, <= 15.0.1.2>= 15.1.0, <= 15.1.0.1
Big Ip Link ControllerApplication
Affected:>= 14.1.0, <= 14.1.2.3>= 15.0.0, <= 15.0.1.2>= 15.1.0, <= 15.1.0.1
Big Ip Local Traffic ManagerApplication
Affected:>= 14.1.0, <= 14.1.2.3>= 15.0.0, <= 15.0.1.2>= 15.1.0, <= 15.1.0.1

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 BIG-IP version
    Run 'tmsh show sys version' or view the version in the BIG-IP Configuration Utility under System > Software Management > Volume Name. Compare the installed version against the affected ranges: 14.1.0-14.1.2.3, 15.0.0-15.0.1.2, 15.1.0-15.1.0.1
    Affected if The installed version falls within any of the affected version ranges
  2. Identify virtual servers with Fallback Host configured
    Run 'tmsh list ltm virtual all one-line' and look for 'fallback host' in the output, or navigate to Local Traffic > Virtual Servers in the Configuration Utility and review each virtual server's settings for a Fallback Host value
    Affected if Any virtual server has a Fallback Host setting configured with a non-empty value
  3. Check for HTTP/2 profile on virtual servers with Fallback Host
    For each virtual server with a Fallback Host, examine the associated HTTP profile (under Request Profile) and determine if it is an HTTP/2 profile. Run 'tmsh list ltm virtual <virtual_name>' to see the full configuration including profiles
    Affected if A virtual server with a Fallback Host also has an HTTP/2 profile assigned on the server side (HTTP/2 profile listed in the virtual server configuration)

The environment is affected if the BIG-IP version is within the affected ranges AND there exists a virtual server that has both a Fallback Host configured and a server-side HTTP/2 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.

From vendor data
Upgrade available Upgrade to a release after 15.1.0.1
Interim mitigation

Upgrade BIG-IP to a version beyond the affected releases (15.1.0.2+, 15.0.1.3+, 14.1.2.4+) or apply the available hotfix. Alternatively, if immediate patching is not feasible, consider removing the Fallback Host configuration from affected virtual servers as a temporary workaround while planning the upgrade.

Fix this in Big Ip Access Policy Manager Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,840
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,544.

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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-2020-5891 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