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Big Ip Access Policy ManagerApplication · F5

CVE-2020-5938

MEDIUM · 6.5 CVSS v3.1 Published 2020-10-29
Fix available
A fix is available. Upgrade to after 13.1.3.4 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable 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 13.1.0-13.1.3.4, 12.1.0-12.1.5.2, and 11.6.1-11.6.5.2, when negotiating IPSec tunnels with configured, authenticated peers, the peer may negotiate a different key length than the BIG-IP configuration would otherwise allow.

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

In affected BIG-IP versions, when establishing IPSec tunnels with authenticated peers, the peer can negotiate a different (weaker) key length than what the BIG-IP configuration specifies, allowing potential cryptographic key length downgrade during tunnel establishment.

MitigationApply the appropriate F5 hotfix or upgrade to a patched version, and review IPSec tunnel configurations to ensure peer settings enforce the intended key lengths.

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:>= 11.6.1, <= 11.6.5.2>= 12.1.0, <= 12.1.5.2>= 13.1.0, <= 13.1.3.4
Big Ip Advanced Firewall ManagerApplication
Affected:>= 11.6.1, <= 11.6.5.2>= 12.1.0, <= 12.1.5.2>= 13.1.0, <= 13.1.3.4
Big Ip Advanced Web Application FirewallApplication
Affected:>= 11.6.1, <= 11.6.5.2>= 12.1.0, <= 12.1.5.2>= 13.1.0, <= 13.1.3.4
Big Ip AnalyticsApplication
Affected:>= 11.6.1, <= 11.6.5.2>= 12.1.0, <= 12.1.5.2>= 13.1.0, <= 13.1.3.4
Big Ip Application Acceleration ManagerApplication
Affected:>= 11.6.1, <= 11.6.5.2>= 12.1.0, <= 12.1.5.2>= 13.1.0, <= 13.1.3.4
Big Ip Application Security ManagerApplication
Affected:>= 11.6.1, <= 11.6.5.2>= 12.1.0, <= 12.1.5.2>= 13.1.0, <= 13.1.3.4
Big Ip Ddos Hybrid DefenderApplication
Affected:>= 11.6.1, <= 11.6.5.2>= 12.1.0, <= 12.1.5.2>= 13.1.0, <= 13.1.3.4
Big Ip Domain Name SystemApplication
Affected:>= 11.6.1, <= 11.6.5.2>= 12.1.0, <= 12.1.5.2>= 13.1.0, <= 13.1.3.4

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

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. Identify installed BIG-IP version
    Run 'tmsh show sys version' or check the BIG-IP GUI under Dashboard to find the base software version
    Affected if The version falls within 11.6.1-11.6.5.2, 12.1.0-12.1.5.2, or 13.1.0-13.1.3.4
  2. Determine if IPSec tunnels are configured
    Review the BIG-IP network configuration for any active IPSec tunnel definitions using tmsh or the configuration utility
    Affected if IPSec tunnels are defined and actively used in the environment
  3. Verify IPSec tunnel authentication settings
    Examine the IPSec tunnel profile or configuration to determine if the peer is using authenticated mode (such as XAuth, Hybrid, or certificate-based authentication)
    Affected if The IPSec peer is configured with authenticated mode which allows key length negotiation
  4. Inspect IPSec transform set or proposal settings
    Check the IPSec configuration for the encryption algorithm and key length settings defined in the transform set or proposal
    Affected if The configuration permits multiple key lengths or weaker algorithms (such as 3DES or AES with 128-bit keys) that could be negotiated down
  5. Review peer proposal enforcement
    Inspect the IPSec policy to see whether the local configuration enforces specific key lengths or allows the peer to select the algorithm
    Affected if The local IPSec policy does not enforce minimum key length requirements and permits the peer to dictate the encryption strength

The environment is affected if the BIG-IP version is within the listed vulnerable ranges AND IPSec tunnels are configured with authenticated peers that can negotiate weaker key lengths than intended.

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 13.1.3.4
Interim mitigation

Apply the appropriate F5 hotfix or upgrade to a patched version, and review IPSec tunnel configurations to ensure peer settings enforce the intended key lengths.

Fix this in Big Ip Access Policy Manager Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,330
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,728.

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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-2020-5938 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