dbcve.org
Secure Email GatewayApplication · Cisco

CVE-2025-20153

MEDIUM · 5.3 CVSS v3.1 Published 2025-02-19
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
62/100
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 email filtering mechanism of Cisco Secure Email Gateway could allow an unauthenticated, remote attacker to bypass the configured rules and allow emails that should have been denied to flow through an affected device.   This vulnerability is due to improper handling of email that passes through an affected device. An attacker could exploit this vulnerability by sending a crafted email through the affected device. A successful exploit could allow the attacker to bypass email filters on the affected device.

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

A vulnerability in the email filtering mechanism of Cisco Secure Email Gateway allows an unauthenticated remote attacker to bypass configured email filtering rules by sending specially crafted emails through the affected device. The vulnerability stems from improper handling of email content passing through the device, enabling malicious emails to flow through instead of being blocked.

MitigationApply the vendor-supplied patch or software update for Cisco Secure Email Gateway when available, and review configured email filtering rules for potential bypass attempts in logs.

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
Secure Email GatewayApplication
Affected:= 13.0.0-392= 13.0.5-007= 13.5.1-277= 13.5.4-038= 14.0.0-698= 14.2.0-620= 14.2.1-020= 14.3.0-032= 15.0.0-104= 15.0.1-030= 15.0.3-002= 15.5.0-048

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
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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. Identify installed Cisco Secure Email Gateway version
    Log into the appliance CLI and run the command: `version` or `show version`. Alternatively, access the web interface and navigate to System Administration > Updates to view the current software version.
    Affected if The displayed version matches one of the following: 13.0.0-392, 13.0.5-007, 13.5.1-277, 13.5.4-038, 14.0.0-698, 14.2.0-620, 14.2.1-020, 14.3.0-032, 15.0.0-104, 15.0.1-030, 15.0.3-002, or 15.5.0-048
  2. Verify email filtering rules are active
    Log into the web interface and navigate to Mail Policies > Incoming Mail Policies or use CLI command: `show policy` to view configured filtering rules.
    Affected if Email filtering policies are defined and enabled on the gateway, indicating the bypass vulnerability could apply to protected mail flows
  3. Review mail logs for filtered messages that were delivered
    Use CLI command: `grep -i "bypass" /var/log/maillog` or navigate to Monitor > Message Tracking in the web interface to search for messages that passed through despite matching filter rules. Look for anomalies in message delivery logs around the time of potential exploit attempts.
    Affected if Messages matching known filter criteria were delivered when they should have been quarantined or blocked, suggesting potential bypass activity
  4. Check for recent mail flow anomalies
    Navigate to Monitor > Traffic Statistics or use CLI command: `grep "DELIVERED" /var/log/maillog | tail -n 100` to review recent delivered messages and compare against expected filtering behavior.
    Affected if Unusual patterns exist such as unexpected deliveries or spikes in message volume that correlate with the affected version being deployed

A system is affected if it runs any of the listed versions AND has email filtering rules enabled, as the vulnerability allows specially crafted emails to bypass those rules.

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 patch or software update for Cisco Secure Email Gateway when available, and review configured email filtering rules for potential bypass attempts in logs.

Fix this in Secure Email Gateway Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
15.0 hours of engineering $2,560
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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-2025-20153 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