Email Security Appliance FirmwareOperating system · Cisco
CVE-2019-12706
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 Sender Policy Framework (SPF) functionality of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass the configured user filters on an affected device. The vulnerability exists because the affected software insufficiently validates certain incoming SPF messages. An attacker could exploit this vulnerability by sending a custom SPF packet to an affected device. A successful exploit could allow the attacker to bypass the configured header 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 Email Security Appliance (ESA) AsyncOS software allows unauthenticated remote attackers to bypass configured header filters by sending specially crafted SPF packets. The flaw is in insufficient validation of incoming SPF messages, which can allow malicious content to pass through the device undetected.
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 Appliance FirmwareOperating system
< 13.5.0CVSS 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 device as Cisco ESAConfirm the device is a Cisco Email Security Appliance by checking the product model number in the hardware label or administrative interfaceAffected if The device is not a Cisco ESA - this CVE does not apply
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Check AsyncOS firmware versionAccess the ESA administrative web interface or CLI and navigate to System Administration > Software Upgrade or use the 'version' command in CLI to display the running AsyncOS versionAffected if The installed AsyncOS firmware version is any version before 13.5.0 (e.g., 13.0.0, 12.5.x, etc.)
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Verify header filters are configuredIn the ESA web interface, go to Mail Policies > Inbound Message Filters or use the 'filters' CLI command to list configured header filtersAffected if Header filters are actively configured and processing incoming messages - the bypass affects these filters
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Confirm SPF checking is enabledIn the ESA web interface, go to Mail Policies > Sender Reputation Settings or Virtual Gateway settings and verify if SPF verification/checking is enabled for incoming messagesAffected if SPF verification is enabled - the vulnerability allows specially crafted SPF packets to bypass header filters when SPF validation is active
The environment is affected if running Cisco ESA with AsyncOS firmware versions prior to 13.5.0 with header filters configured and SPF checking 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 data13.5.0
Apply the vendor patch from Cisco for AsyncOS software. Review and potentially augment header filters as a defense-in-depth measure while the patch is being deployed.
Fix this in Email Security Appliance Firmware
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-12706 — 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-2019-12706 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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