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Email Security ApplianceApplication · Cisco

CVE-2019-1947

HIGH · 8.6 CVSS v3.1 Published 2020-09-23
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
95/100
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 email message filtering feature of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to cause the CPU utilization to increase to 100 percent, causing a denial of service (DoS) condition on an affected device. The vulnerability is due to improper handling of email messages that contain large attachments. An attacker could exploit this vulnerability by sending a malicious email message through the targeted device. A successful exploit could allow the attacker to cause a permanent DoS condition due to high CPU utilization. This vulnerability may require manual intervention to recover the ESA.

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 denial of service vulnerability in Cisco Email Security Appliance (ESA) exists in the email message filtering feature due to improper handling of email messages containing large attachments. An unauthenticated remote attacker can send a malicious email with oversized attachments that causes CPU utilization to spike to 100%, rendering the device permanently unavailable until manual intervention is performed.

MitigationApply the vendor-supplied software patch for Cisco AsyncOS. If immediate patching is not possible, consider implementing email message size limits or rate limiting at the perimeter to reduce exposure to malicious oversized attachments.

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:= 11.1.0-131
AsyncosOperating system
Affected:= 12.1.0-085

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
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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. Confirm Cisco ESA device
    Log into the ESA CLI or web interface and verify the device model is Cisco Email Security Appliance. In CLI, run 'version' or check the web UI dashboard for device type.
    Affected if The device is not a Cisco ESA (the CVE only affects ESA, not other Cisco products).
  2. Check AsyncOS version
    In the ESA CLI, run the 'version' command to display the installed AsyncOS version. Compare this version number against the affected ranges (11.1.0-131 and earlier, 12.1.0-085 and earlier).
    Affected if The installed AsyncOS version is 11.1.0-131 or earlier, OR 12.1.0-085 or earlier.
  3. Verify email message filtering is enabled
    In the ESA web interface, navigate to Mail Policies > Incoming Mail Policies or use CLI command 'filters' to list active message filters. The vulnerability affects the filtering feature, so verify filters are configured.
    Affected if Message filters are active and processing incoming emails (the flaw is triggered when the filtering engine processes emails with oversized attachments).
  4. Inspect attachment size limits
    Check current attachment size limits via CLI command 'attachmentconfig' or in the web interface under Mail Policies > Message Filters > Attachment Settings. Look for max attachment size settings.
    Affected if No attachment size limit is configured, or limits are set very high (unrestricted), allowing oversized attachments to be processed by the filter.

A user is affected if their Cisco ESA runs AsyncOS version 11.1.0-131 or earlier, or 12.1.0-085 or earlier, and has email message filtering enabled without adequate attachment size restrictions.

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 vendor-supplied software patch for Cisco AsyncOS. If immediate patching is not possible, consider implementing email message size limits or rate limiting at the perimeter to reduce exposure to malicious oversized attachments.

Fix this in Email Security Appliance Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA4.0 h
20.0 hours of engineering $3,440
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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-2019-1947 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