Email Security Appliance FirmwareOperating system · Cisco
CVE-2019-15988
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 the 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 · high confidenceA vulnerability in Cisco Email Security Appliance (ESA) allows unauthenticated remote attackers to bypass URL reputation filters due to insufficient input validation of URLs. Attackers can craft malicious URLs in a specific way to evade detection and pass through the ESA device, potentially delivering phishing or malware content to end users.
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
<= 12.5.0CVSS 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
- 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 checksWork through these to decide whether this CVE applies to you.
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Identify the installed Cisco ESA firmware versionAccess the ESA CLI or web interface and navigate to System Administration > Software Updates or use the 'version' command in the CLI to retrieve the current firmware versionAffected if The installed firmware version is 12.5.0 or earlier (any version <= 12.5.0)
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Verify URL reputation filtering is enabledIn the ESA web interface, go to Mail Policies > Inbound URL Filtering and confirm the 'Enable URL Filtering' option is turned on, or use the 'urlfilterconfig' CLI commandAffected if URL reputation filtering is actively enabled on the device
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Review URL filtering logs for potential bypass attemptsUse the ESA log subscriptions or the 'grep' command to search URL logs (typically found in URL Logs or Message Tracking) for anomalous URL patterns or unusually high volumes of URLs passing through without blockingAffected if Logs show URLs passing through that would normally be blocked by reputation filters, or unexpected URL patterns are detected
You are affected if your Cisco ESA runs firmware version 12.5.0 or earlier AND has URL reputation filtering enabled, as the bypass vulnerability exists in those configurations.
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 vendor-supplied patch/update to Cisco AsyncOS Software that addresses the input validation weakness in URL reputation filters. Ensure URL filtering policies are reviewed and tested after the update.
Fix this in Email Security Appliance Firmware
Scoped from the published advisory
- Consultation4.0 h
- Implementation6.0 h
- Testing4.0 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 $4,544.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-15988 — 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-2019-15988 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