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Email Security Appliance FirmwareOperating system · Cisco

CVE-2017-12309

MEDIUM · 5.3 CVSS v3.0 Published 2017-11-16
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 Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to conduct a HTTP response splitting attack. The vulnerability is due to the failure of the application or its environment to properly sanitize input values. An attacker could exploit this vulnerability by injecting malicious HTTP headers, controlling the response body, or splitting the response into multiple responses. An exploit could allow the attacker to perform cross-site scripting attacks, cross-user defacement, web cache poisoning, and similar exploits. Cisco Bug IDs: CSCvf16705.

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 confidence

The Cisco Email Security Appliance (ESA) contains an HTTP response splitting vulnerability where the application fails to properly sanitize input values. An unauthenticated remote attacker can inject malicious HTTP headers by controlling input, allowing them to split HTTP responses and potentially perform cross-site scripting (XSS) attacks, cross-user defacement, web cache poisoning, and similar exploits.

MitigationApply the Cisco patch for bug CSCvf16705, which is the vendor-supplied fix for this vulnerability. As a critical email security device, the ESA should be updated during a planned maintenance window with thorough testing of email flow and web interface functionality.

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
Affected:= 10.0.2-020= 11.0.0-105

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:3.0/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. Verify ESA web interface is accessible
    Confirm the Cisco ESA web interface (HTTPS/HTTP) is reachable from network locations. This can be done by attempting to access the device's management IP on ports 80/443 or checking firewall rules that allow HTTP/HTTPS traffic to the ESA.
    Affected if The ESA web interface is exposed to untrusted networks (including the internet) without proper network segmentation or authentication barriers.
  2. Identify the installed ESA firmware version
    Log into the ESA CLI and run the command 'version' or 'show version' to display the current firmware version. Alternatively, access the web interface and navigate to System Administration > Configuration Summary to view the version information.
    Affected if The installed version matches exactly 10.0.2-020 or 11.0.0-105, or falls within a release train that includes these specific vulnerable versions.
  3. Confirm ESA is processing HTTP traffic
    Check if the ESA is configured to accept HTTP connections. In the web interface, go to Network > HTTP Settings or use the CLI command 'httpconfig' to review HTTP listener settings. Verify if HTTP services are enabled.
    Affected if HTTP (port 80) or HTTPS (port 443) services are enabled and the ESA is actively accepting HTTP connections from users or external systems.
  4. Review HTTP response headers for injection
    Send a crafted HTTP request with carriage return and line feed characters (for example, in a parameter value) to the ESA web interface and observe the response headers. Use a tool like curl or Burp Suite to capture and inspect the full HTTP response.
    Affected if The HTTP response contains multiple response codes (evidenced by multiple Set-Cookie, Location, or other header lines) or displays arbitrary user-supplied content in the response headers.

The environment is affected if the ESA firmware version matches 10.0.2-020 or 11.0.0-105 (or is in the same release train) and the web interface HTTP service is enabled and accessible.

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 Cisco patch for bug CSCvf16705, which is the vendor-supplied fix for this vulnerability. As a critical email security device, the ESA should be updated during a planned maintenance window with thorough testing of email flow and web interface functionality.

Fix this in Email Security Appliance Firmware Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,770
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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-2017-12309 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
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