Email Security ApplianceApplication · Cisco
CVE-2020-3133
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 · uneditedA vulnerability in the email message scanning of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass configured filters on the device. The vulnerability is due to improper validation of incoming emails. An attacker could exploit this vulnerability by sending a crafted email message to a recipient protected by the ESA. A successful exploit could allow the attacker to bypass the configured content filters, which could allow malicious content to pass through the 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 · high confidenceA vulnerability in Cisco AsyncOS Software's email message scanning allows unauthenticated remote attackers to bypass configured content filters on the Email Security Appliance by sending specially crafted email messages with improper validation that exploits the scanning logic.
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
< 13.0CVSS 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
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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 checksWork through these to decide whether this CVE applies to you.
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Identify the Cisco Email Security Appliance modelCheck the device web interface under System Administration > Product Identification, or run the 'version' command in the CLI to confirm the hardware model and software versionAffected if The device is not a Cisco Email Security Appliance (ESA)
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Determine the installed AsyncOS versionRun the 'version' command in the ESA CLI, or check the web interface under System Administration > Software Upgrade. Compare the displayed version number to the 13.0 releaseAffected if The AsyncOS version is 13.0 or higher (versions below 13.0 are affected)
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Verify content filters are configuredCheck the ESA web interface under Mail Policies > Incoming Mail Policies, or run the 'filters' command in the CLI to list active content filtersAffected if No content filters are enabled - the bypass vulnerability has no impact without configured filters
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Review mail logs for signs of filter bypassExamine the ESA mail logs (Mail Logs > Message Tracking in the web interface, or via the 'grep' or 'tail' commands in the CLI) for patterns where expected content-filtered messages were not quarantined or blockedAffected if Messages with suspicious content were delivered despite matching content filter rules
A Cisco ESA running AsyncOS versions below 13.0 with active content filters is vulnerable to CVE-2020-3133 if specially crafted emails bypass filter rules.
Generated from the published advisory. Verify against your own configuration.
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 data13.0
Apply Cisco's security patches for CVE-2020-3133; until patched, implement additional email filtering layers or manual inspection of suspicious emails as compensating controls.
Fix this in Email Security Appliance
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-3133 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-3133 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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