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Big Ip Local Traffic ManagerApplication · F5

CVE-2016-6876

HIGH · 7.5 CVSS v3.0 Published 2016-09-07
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
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
The RESOLV::lookup iRule command in F5 BIG-IP LTM, APM, ASM, and Link Controller 10.2.1 through 10.2.4, 11.2.1, 11.4.x, 11.5.x before 11.5.4 HF2, 11.6.x before 11.6.1, and 12.0.0 before HF3; BIG-IP AAM, AFM, and PEM 11.4.x, 11.5.x before 11.5.4 HF2, 11.6.x before 11.6.1, and 12.0.0 before HF3; BIG-IP Analytics 11.2.1, 11.4.x, 11.5.x before 11.5.4 HF2, 11.6.x before 11.6.1, and 12.0.0 before HF3; BIG-IP DNS 12.0.0 before HF3; BIG-IP Edge Gateway, WebAccelerator, and WOM 10.2.1 through 10.2.4 and 11.2.1; BIG-IP GTM 10.2.1 through 10.2.4, 11.2.1, 11.4.x, 11.5.x before 11.5.4 HF2, and 11.6.x before 11.6.1; and BIG-IP PSM 10.2.1 through 10.2.4 and 11.4.0 through 11.4.1 allows remote DNS servers to cause a denial of service (CPU consumption or Traffic Management Microkernel crash) via a crafted PTR response.

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

The RESOLV::lookup iRule command in F5 BIG-IP products contains a denial-of-service vulnerability. A remote DNS server can send a crafted PTR response that triggers either excessive CPU consumption or a crash of the Traffic Management Microkernel (TMM), causing service disruption.

MitigationApply the appropriate F5 hotfix (11.5.4 HF2, 11.6.1, 12.0.0 HF3 or later) to affected products. Additionally, restrict which DNS servers can respond to iRule DNS lookups through network segmentation or ACLs.

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 Local Traffic ManagerApplication
Affected:= 10.2.1= 10.2.2= 10.2.3= 10.2.4= 11.2.1= 11.4.0= 11.4.1= 11.5.0= 11.5.1= 11.5.2= 11.5.3= 11.5.4
Big Ip WebacceleratorApplication
Affected:= 10.2.1= 10.2.2= 10.2.3= 10.2.4= 11.2.1
Big Ip Application Acceleration ManagerApplication
Affected:= 11.4.0= 11.4.1= 11.5.0= 11.5.1= 11.5.2= 11.5.3= 11.5.4= 11.6.0= 12.0.0
Big Ip Global Traffic ManagerApplication
Affected:= 10.2.1= 10.2.2= 10.2.3= 10.2.4= 11.2.1= 11.4.0= 11.4.1= 11.5.0= 11.5.1= 11.5.2= 11.5.3= 11.5.4
Big Ip Link ControllerApplication
Affected:= 10.2.1= 10.2.2= 10.2.3= 10.2.4= 11.2.1= 11.4.0= 11.4.1= 11.5.0= 11.5.1= 11.5.2= 11.5.3= 11.5.4
Big Ip Advanced Firewall ManagerApplication
Affected:= 11.4.0= 11.4.1= 11.5.0= 11.5.1= 11.5.2= 11.5.3= 11.5.4= 11.6.0= 12.0.0
Big Ip Protocol Security ModulePlugin / extension
Affected:= 10.2.1= 10.2.2= 10.2.3= 10.2.4= 11.4.0= 11.4.1
Big Ip Wan Optimization ManagerApplication
Affected:= 10.2.1= 10.2.2= 10.2.3= 10.2.4= 11.2.1

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:3.0/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed BIG-IP version
    Run 'tmsh show sys version' or 'bigtop -v' from the command line to obtain the software version
    Affected if The version matches one of the listed affected versions (10.2.1-11.5.4 for LTM/GTM/LC, 10.2.1-11.2.1 for WebAccelerator/WOM, 11.4.0-12.0.0 for AAM/AFM, 10.2.1-11.4.1 for PSM)
  2. Identify installed product modules
    Run 'tmsh show sys module' or check the system dashboard to see which modules are licensed (LTM, GTM, AAM, AFM, LC, WebAccelerator, PSM, WOM)
    Affected if Any of the affected modules (LTM, GTM, LC, WebAccelerator, AAM, AFM, PSM, WOM) are installed on an affected version
  3. Check for RESOLV::lookup iRules
    Run 'tmsh list ltm rule all' to list all iRules, then search for 'RESOLV::lookup' in the output using grep or manual inspection
    Affected if Any iRule contains the RESOLV::lookup command, which is the vulnerable code path
  4. Verify iRule is actively applied
    Run 'tmsh list ltm virtual all' and cross-reference with the iRules found in step 3 to confirm the RESOLV::lookup iRules are assigned to virtual servers
    Affected if The RESOLV::lookup iRule is assigned to an active virtual server, making it reachable to DNS responses
  5. Check DNS server exposure
    Review network configuration to determine which DNS servers can send responses to the BIG-IP device, particularly PTR records
    Affected if DNS servers outside the trusted network can send responses to the BIG-IP system

You are affected if you run an affected product version with an active iRule using RESOLV::lookup that can receive DNS responses from untrusted or external DNS servers.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the appropriate F5 hotfix (11.5.4 HF2, 11.6.1, 12.0.0 HF3 or later) to affected products. Additionally, restrict which DNS servers can respond to iRule DNS lookups through network segmentation or ACLs.

Fix this in Big Ip Local Traffic Manager Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing3.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,750
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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-2016-6876 in production — separate from our analysis above.

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What this is

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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