dbcve.org
Email Security Appliance FirmwareOperating system · Cisco

CVE-2016-6406

CRITICAL · 9.8 CVSS v3.0 Published 2016-09-22
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
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
Cisco IronPort AsyncOS 9.1.2-023, 9.1.2-028, 9.1.2-036, 9.7.2-046, 9.7.2-047, 9.7.2-054, 10.0.0-124, and 10.0.0-125 on Email Security Appliance (ESA) devices, when Enrollment Client before 1.0.2-065 is installed, allows remote attackers to obtain root access via a connection to the testing/debugging interface, aka Bug ID CSCvb26017.

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

Cisco IronPort Email Security Appliance (ESA) devices running specific AsyncOS versions (9.1.2-023 through 10.0.0-125) with Enrollment Client before 1.0.2-065 contain a vulnerability in the testing/debugging interface that allows remote unauthenticated attackers to gain root access, effectively giving them complete control over the appliance.

MitigationUpgrade AsyncOS to a patched version and ensure Enrollment Client is updated to 1.0.2-065 or later. Additionally, disable or restrict access to any testing/debugging interfaces on production ESA devices if not already done.

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
Email Security Appliance FirmwareOperating system
Affected:= 9.1.2-023= 9.1.2-028= 9.1.2-036= 9.7.2-046= 9.7.2-047= 9.7.2-054= 10.0.0-124= 10.0.0-125

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
High
Integrity
High
Availability
High

CVSS:3.0/AV:N/AC:L/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. Check AsyncOS firmware version
    Log into the ESA CLI and run the 'version' command, or access the web interface and navigate to System Administration > Software Updates to view the installed AsyncOS version
    Affected if The installed version matches exactly 9.1.2-023, 9.1.2-028, 9.1.2-036, 9.7.2-046, 9.7.2-047, 9.7.2-054, 10.0.0-124, or 10.0.0-125
  2. Check Enrollment Client version
    Access the ESA web interface and navigate to System Administration > Enrollment or check the installed software components list for the Enrollment Client version
    Affected if Enrollment Client version exists and is earlier than 1.0.2-065, or if no version is displayed (indicating an older installation)
  3. Verify testing/debugging interface exposure
    Check the ESA configuration for any enabled testing, debugging, or diagnostic interfaces. In CLI, use 'show interface' or check access lists. In web UI, review Network > Access Lists or similar security settings
    Affected if A testing or debugging interface (such as a diagnostic port, test API, or debug service) is enabled and reachable from the network
  4. Confirm ESA appliance model
    Identify the device model via CLI command 'arch' or via the web interface System Overview page
    Affected if The device is a Cisco IronPort Email Security Appliance or Cisco ESA model running the vulnerable AsyncOS versions listed above

You are affected if your ESA runs any of the eight specific AsyncOS versions (9.1.2-023 through 10.0.0-125) AND has the Enrollment Client version below 1.0.2-065 AND has an accessible testing/debugging interface.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade AsyncOS to a patched version and ensure Enrollment Client is updated to 1.0.2-065 or later. Additionally, disable or restrict access to any testing/debugging interfaces on production ESA devices if not already done.

Recommended fix Moderate confidence

ESA firmware beyond 10.0.0-125 or Enrollment Client 1.0.2-065 or later

  1. Identify the currently installed Enrollment Client version on the ESA device
  2. If Enrollment Client version is before 1.0.2-065, upgrade to version 1.0.2-065 or later
  3. Alternatively, upgrade ESA firmware to a version beyond 10.0.0-125 which contains the fix
  4. After upgrade, verify the testing/debugging interface is disabled or properly secured
  5. Confirm root access is no longer obtainable via the debugging interface
Caveat Review Cisco release notes for potential compatibility issues when upgrading ESA firmware or Enrollment Client

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Email Security Appliance Firmware 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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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-2016-6406 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