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Adaptive Security Appliance SoftwareOperating system · Cisco

CVE-2016-6432

HIGH · 8.1 CVSS v3.0 Published 2016-10-27
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
90/100
Remediation priority · Urgent
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
A vulnerability in the Identity Firewall feature of Cisco ASA Software before 9.6(2.1) could allow an unauthenticated, remote attacker to cause a reload of the affected system or to remotely execute code. The vulnerability is due to a buffer overflow in the affected code area. An attacker could exploit this vulnerability by sending a crafted NetBIOS packet in response to a NetBIOS probe sent by the ASA software. An exploit could allow the attacker to execute arbitrary code and obtain full control of the system or cause a reload of the affected system. Note: Only traffic directed to the affected system can be used to exploit this vulnerability. This vulnerability affects systems configured in routed and transparent firewall mode and in single or multiple context mode. This vulnerability can be triggered by IPv4 traffic.

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

A buffer overflow vulnerability exists in the Identity Firewall feature of Cisco ASA Software before version 9.6(2.1). The flaw is triggered when an unauthenticated, remote attacker sends a crafted NetBIOS packet in response to a NetBIOS probe initiated by the ASA software. Successful exploitation allows arbitrary code execution with full system control or can cause a denial of service via system reload. Only traffic directed to the affected ASA system can trigger this issue, and the vulnerability affects both routed and transparent firewall modes in single or multiple context configurations.

MitigationUpgrade Cisco ASA Software to version 9.6(2.1) or later. If immediate upgrade is not feasible, consider disabling the Identity Firewall feature or implementing network segmentation to limit exposure to directed NetBIOS traffic.

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
Adaptive Security Appliance SoftwareOperating system
Affected:= 8.4.0= 8.4.2= 8.4.2.1= 8.4.2.8= 8.4.3= 8.4.3.8= 8.4.3.9= 8.4.4= 8.4.4.1= 8.4.4.3= 8.4.4.5= 8.4.4.9

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
High
Availability
High

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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. Determine the Cisco ASA software version
    Connect to the ASA CLI and execute the 'show version' command. Look for the software version number in the output.
    Affected if The version matches one of the affected versions: 8.4.0, 8.4.2, 8.4.2.1, 8.4.2.8, 8.4.3, 8.4.3.8, 8.4.3.9, 8.4.4, 8.4.4.1, 8.4.4.3, 8.4.4.5, 8.4.4.9, or is earlier than 9.6(2.1).
  2. Verify if Identity Firewall feature is enabled
    Execute 'show running-config | include identity' or 'show running-config object-group network' to check for Identity Firewall-related configuration objects. Also run 'show ip audit' or check the access rules for identity-related policies.
    Affected if Identity Firewall feature is configured and enabled on the ASA device.
  3. Confirm NetBIOS inspection is active
    Run 'show running-config inspect netbios' or 'show service-policy' to determine if NetBIOS inspection is enabled as part of the Identity Firewall functionality.
    Affected if NetBIOS inspection is enabled in conjunction with Identity Firewall, making the device vulnerable to crafted NetBIOS packet responses.

You are affected if your ASA runs version 8.4.x or any version earlier than 9.6(2.1) AND has the Identity Firewall feature enabled with NetBIOS inspection active.

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

Upgrade Cisco ASA Software to version 9.6(2.1) or later. If immediate upgrade is not feasible, consider disabling the Identity Firewall feature or implementing network segmentation to limit exposure to directed NetBIOS traffic.

Fix this in Adaptive Security Appliance Software Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing6.0 h
  • Review / QA3.0 h
19.0 hours of engineering $3,320
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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-2016-6432 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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