dbcve.org
Email Security ApplianceApplication · Cisco

CVE-2019-1905

MEDIUM · 5.8 CVSS v3.0 Published 2019-06-20
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
67/100
Remediation priority · Elevated
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 GZIP decompression engine of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass configured content filters on the device. The vulnerability is due to improper validation of GZIP-formatted files. An attacker could exploit this vulnerability by sending a malicious file inside a crafted GZIP-compressed file. A successful exploit could allow the attacker to bypass configured content filters that would normally drop the email.

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 · moderate confidence

The vulnerability exists in the GZIP decompression engine of Cisco Email Security Appliance (ESA) running AsyncOS software. The engine does not properly validate GZIP-formatted files, allowing an attacker to embed malicious file content inside a crafted GZIP archive that bypasses configured content filters designed to detect and drop dangerous attachments.

MitigationApply the relevant Cisco security patch for CVE-2019-1905 to the AsyncOS software. No configuration-based workarounds are mentioned in the advisory; upgrading to a fixed AsyncOS version is the primary remediation.

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:= 11.1.2= 12.0.0

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
Low
Availability
None

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

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 device is a Cisco Email Security Appliance
    Log into the ESA CLI or web interface and verify the device model is an Email Security Appliance. In the CLI, run 'show hardware' or check the web UI dashboard for the appliance type.
    Affected if The device is not a Cisco ESA (this CVE only affects ESA models).
  2. Check the AsyncOS version
    In the ESA CLI, run 'version' or 'show version' to display the installed AsyncOS software version. Alternatively, check the web UI under System Administration > Software Upgrade.
    Affected if The installed version is 11.1.2 or 12.0.0 specifically, or falls within the affected version range if additional versions are listed in the Cisco advisory.
  3. Verify content filters are configured for attachment detection
    In the ESA web UI, navigate to Mail Policies > Incoming Mail Policies or Outgoing Mail Policies. Check if any content filters are enabled that include attachment type conditions (such as 'attachment file type' or 'attachment name' rules). In CLI, use 'filters' command to list active filters.
    Affected if Content filters detecting dangerous attachment types are configured and enabled on incoming or outgoing mail policies.
  4. Confirm GZIP-compressed attachments are being processed
    Review the content filter conditions to see if they evaluate attachment content after decompression. Check if GZIP archives are being accepted and decompressed by the ESA. Use ' TRACE' or 'policy' debug commands to observe how GZIP attachments are being handled by the filter engine.
    Affected if The ESA is decompressing GZIP attachments and applying content filters to the decompressed content, as this is the vulnerable code path.

The environment is affected if the device is a Cisco ESA running AsyncOS version 11.1.2 or 12.0.0 (or an affected version range) with content filters configured to detect dangerous attachments, and the ESA is processing GZIP-compressed files through those filters.

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 relevant Cisco security patch for CVE-2019-1905 to the AsyncOS software. No configuration-based workarounds are mentioned in the advisory; upgrading to a fixed AsyncOS version is the primary remediation.

Fix this in Email Security Appliance 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
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,544.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2019-1905 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2019-1905 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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