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Big Ip Access Policy ManagerApplication · F5

CVE-2020-5929

MEDIUM · 5.9 CVSS v3.1 Published 2020-09-25
Fix available
A fix is available. Upgrade to 11.6.2 / 12.1.2 or later.
See remediation →
68/100
Remediation priority · Elevated
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
In versions 13.0.0-13.0.0 HF2, 12.1.0-12.1.2 HF1, and 11.6.1-11.6.2, BIG-IP platforms with Cavium Nitrox SSL hardware acceleration cards, a Virtual Server configured with a Client SSL profile, and using Anonymous (ADH) or Ephemeral (DHE) Diffie-Hellman key exchange and Single DH use option not enabled in the options list may be vulnerable to crafted SSL/TLS Handshakes that may result with a PMS (Pre-Master Secret) that starts in a 0 byte and may lead to a recovery of plaintext messages as BIG-IP TLS/SSL ADH/DHE sends different error messages acting as an oracle. Similar error messages when PMS starts with 0 byte coupled with very precise timing measurement observation may also expose this vulnerability.

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

BIG-IP platforms with Cavium Nitrox SSL hardware acceleration cards running affected versions (13.0.0-13.0.0 HF2, 12.1.0-12.1.2 HF1, 11.6.1-11.6.2) are vulnerable when a Virtual Server uses a Client SSL profile configured with Anonymous (ADH) or Ephemeral (DHE) Diffie-Hellman key exchange WITHOUT the 'Single DH use' option enabled. Crafted SSL/TLS handshakes can cause the Pre-Master Secret (PMS) to begin with a 0 byte, and the different error messages (or timing differences) sent by BIG-IP's TLS/SSL ADH/DHE implementation serve as an oracle, enabling recovery of plaintext messages through a variant of the Lucky Thirteen or similar timing attack.

MitigationEnable the 'Single DH use' option in the Client SSL profile options list, or preferably disable ADH/DHE cipher suites entirely and use ephemeral elliptic curve Diffie-Hellman (ECDHE) key exchange instead.

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, < 11.6.2>= 12.1.0, < 12.1.2= 11.6.2= 12.1.2= 13.0.0
Big Ip Advanced Firewall ManagerApplication
Affected:>= 11.6.1, < 11.6.2>= 12.1.0, < 12.1.2= 11.6.2= 12.1.2= 13.0.0
Big Ip Advanced Web Application FirewallApplication
Affected:>= 11.6.1, < 11.6.2>= 12.1.0, < 12.1.2= 11.6.2= 12.1.2= 13.0.0
Big Ip AnalyticsApplication
Affected:>= 11.6.1, < 11.6.2>= 12.1.0, < 12.1.2= 11.6.2= 12.1.2= 13.0.0
Big Ip Application Acceleration ManagerApplication
Affected:>= 11.6.1, < 11.6.2>= 12.1.0, < 12.1.2= 11.6.2= 12.1.2= 13.0.0
Big Ip Application Security ManagerApplication
Affected:>= 11.6.1, < 11.6.2>= 12.1.0, < 12.1.2= 11.6.2= 12.1.2= 13.0.0
Big Ip Ddos Hybrid DefenderApplication
Affected:>= 11.6.1, < 11.6.2>= 12.1.0, < 12.1.2= 11.6.2= 12.1.2= 13.0.0
Big Ip Domain Name SystemApplication
Affected:>= 11.6.1, < 11.6.2>= 12.1.0, < 12.1.2= 11.6.2= 12.1.2= 13.0.0

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

CVSS:3.1/AV:N/AC:H/PR:N/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. Check BIG-IP version
    Run `tmsh show sys version` or view System > Software Information in the GUI
    Affected if Version is 11.6.1, 11.6.2, 12.1.0, 12.1.1, 12.1.2, or 13.0.0 (or between 13.0.0 and 13.0.0 HF2 if hotfixes are listed)
  2. Verify Cavium Nitrox SSL hardware acceleration card is present
    Run `tmsh show sys hardware` and look for Cavium Nitrox or similar SSL accelerator module in the hardware inventory
    Affected if The system has a Cavium Nitrox SSL hardware acceleration card installed
  3. Identify Client SSL profiles using ADH or DHE ciphers
    Run `tmsh list ltm profile client-ssl all` and inspect the `ciphers` or `cipher-group` settings for ADH or DHE cipher strings
    Affected if Any Client SSL profile contains Anonymous DH (ADH) or standard DHE cipher suites
  4. Check if Single DH use option is disabled
    For each Client SSL profile using ADH/DHE, run `tmsh list ltm profile client-ssl <profile_name>` and look for the `single-dh-use` setting
    Affected if The profile uses ADH or DHE ciphers AND single-dh-use is set to `disabled` or not present (default is disabled)

You are affected if your BIG-IP version is in the affected list, has a Cavium Nitrox SSL accelerator, and you have a Client SSL profile using ADH or DHE ciphers with Single DH use disabled.

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 11.6.2 / 12.1.2 or later
Fixed in 11.6.212.1.2
Interim mitigation

Enable the 'Single DH use' option in the Client SSL profile options list, or preferably disable ADH/DHE cipher suites entirely and use ephemeral elliptic curve Diffie-Hellman (ECDHE) key exchange instead.

Fix this in Big Ip Access Policy Manager Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
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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-2020-5929 in production — separate from our analysis above.

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What this is

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