AsyncosOperating system · Cisco
CVE-2020-3568
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 antispam protection mechanisms of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass the URL reputation filters on an affected device. The vulnerability is due to insufficient input validation of URLs. An attacker could exploit this vulnerability by crafting a URL in a particular way. A successful exploit could allow the attacker to bypass the URL reputation filters that are configured for the affected device, which could allow malicious URLs 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 · moderate confidenceA vulnerability in Cisco Email Security Appliance's antispam mechanism allows specially crafted URLs to bypass reputation filters due to insufficient input validation. An unauthenticated remote attacker can exploit this by creating URLs in a particular way that evade the device's URL filtering logic, permitting malicious URLs to pass through the ESA unchecked.
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
AsyncosOperating system
<= 13.5.2CVSS 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:3.1/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 checksWork through these to decide whether this CVE applies to you.
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Identify the device and AsyncOS versionLog into the ESA CLI and run the command: show version. This displays the AsyncOS version, build, and model information.Affected if The AsyncOS version listed is 13.5.2 or lower.
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Confirm the device is a Cisco Email Security ApplianceFrom the show version output, verify the model field shows an ESA series device (e.g., C100, C300, C600).Affected if The device is an ESA model and the AsyncOS version is <= 13.5.2.
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Verify URL reputation filtering is enabledIn the ESA web interface, navigate to Security Services > IronPort Anti-Spam > Enable. Alternatively, use CLI: show policy config. Check if URL reputation filtering or IronPort Anti-Spam is turned on.Affected if URL reputation filters are enabled and the AsyncOS version is <= 13.5.2.
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Inspect URL filtering policiesIn the web interface, go to Mail Policies > Incoming Mail Policies > and review the URL Filtering settings for each policy. Check if 'Use URL Reputation' or 'Use URL Category' is enabled.Affected if A mail policy has URL reputation filtering enabled on an affected AsyncOS version.
The environment is affected if the Cisco ESA is running AsyncOS version 13.5.2 or lower AND has URL reputation filtering or antispam scanning enabled.
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 dataApply the relevant Cisco security update for CVE-2020-3568; alternatively, supplement URL reputation filters with additional email security controls or supplemental URL analysis solutions.
Fix this in Asyncos
Scoped from the published advisory
- Consultation3.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-3568 — 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-2020-3568 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
- No spam, self-promotion, credentials, or personal data