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Email Security ApplianceApplication · Cisco

CVE-2016-1481

HIGH · 7.5 CVSS v3.0 Published 2016-10-28
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
A vulnerability in the email message filtering feature of Cisco AsyncOS Software for Cisco Email Security Appliances could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.Affected Products: This vulnerability affects all releases prior to the first fixed release of Cisco AsyncOS Software for Cisco Email Security Appliances, both virtual and hardware appliances, if the software is configured to apply a message filter that contains certain rules. More Information: CSCux59873. Known Affected Releases: 8.5.6-106 9.1.0-032 9.7.0-125. Known Fixed Releases: 9.1.1-038 9.7.1-066.

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 vulnerability in the email message filtering feature of Cisco AsyncOS Software for Cisco Email Security Appliances allows an unauthenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability is triggered when the device is configured to apply a message filter containing certain rules, which can be exploited to crash the filtering process or the entire appliance.

MitigationUpgrade Cisco AsyncOS Software to the fixed releases (9.1.1-038, 9.7.1-066 or later). As a temporary workaround, review and modify message filters that contain the problematic rules identified in CSCux59873.

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 ApplianceApplication
Affected:= 8.5.0-000= 8.5.0-er1-198= 8.5.6-052= 8.5.6-073= 8.5.6-074= 8.5.6-106= 8.5.6-113= 8.5.7-042= 8.6.0= 8.6.0-011= 8.9.0= 8.9.1-000

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. Determine Cisco Email Security Appliance AsyncOS version
    Log into the ESA CLI and run the 'version' command, or access the web interface and check System Administration > System Upgrade for the installed AsyncOS version.
    Affected if The installed version matches one of the affected versions: 8.5.0-000, 8.5.0-er1-198, 8.5.6-052, 8.5.6-073, 8.5.6-074, 8.5.6-106, 8.5.6-113, 8.5.7-042, 8.6.0, 8.6.0-011, 8.9.0, or 8.9.1-000.
  2. Verify message filters are configured
    Log into the ESA web interface and navigate to Mail Policies > Message Filters, or use the CLI command 'filters' to list configured message filters.
    Affected if One or more message filters are defined and enabled on the appliance.
  3. Identify message filters with potentially problematic rules
    Review the list of message filters and examine each filter's action and rule definitions. Look for filters that contain complex or recursive rule structures that could trigger the filtering process crash. Document the specific rules and actions configured in each filter.
    Affected if Message filters contain rules that match the pattern described in Cisco bug ID CSCux59873 (the specific problematic filter rules).

You are affected if your appliance runs a vulnerable AsyncOS version AND has message filters with the problematic rules configured and actively applied to mail flow.

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 AsyncOS Software to the fixed releases (9.1.1-038, 9.7.1-066 or later). As a temporary workaround, review and modify message filters that contain the problematic rules identified in CSCux59873.

Fix this in Email Security Appliance Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 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-2016-1481 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