iOSOperating system · Cisco
CVE-2019-12652
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 ingress packet processing function of Cisco IOS Software for Cisco Catalyst 4000 Series Switches could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to improper resource allocation when processing TCP packets directed to the device on specific Cisco Catalyst 4000 Series Switches. An attacker could exploit this vulnerability by sending crafted TCP streams to an affected device. A successful exploit could cause the affected device to run out of buffer resources, impairing operations of control plane and management plane protocols, resulting in a DoS condition. This vulnerability can be triggered only by traffic that is destined to an affected device and cannot be exploited using traffic that transits an affected 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 the ingress packet processing function of Cisco IOS Software for Cisco Catalyst 4000 Series Switches allows an unauthenticated remote attacker to cause a DoS condition by sending crafted TCP packets to the device. The vulnerability stems from improper resource allocation when processing these TCP packets, causing the device to exhaust buffer resources and impair control plane and management plane protocols.
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
iOSOperating system
= 15.2\(3\)e1= 15.2\(4\)e3CVSS 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
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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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Confirm device is a Catalyst 4000 Series SwitchLog into the device and run 'show version' or 'show inventory' to identify the model number. Look for Catalyst 4000, 4500, or 4500-X series switches.Affected if The device model matches the Catalyst 4000 Series family (such as Catalyst 4500 or 4500-X)
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Retrieve the Cisco IOS software versionRun the command 'show version' on the device CLI. Locate the line that displays the IOS version, typically labeled 'Cisco IOS Software' or similar, followed by a version string like 15.2(3)e1.Affected if The device is running Cisco IOS software
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Compare installed version against affected releasesExamine the version string obtained from 'show version'. The affected versions are exactly 15.2(3)e1 and 15.2(4)e3. Compare your installed version to these two specific versions.Affected if The installed Cisco IOS version is exactly 15.2(3)e1 or exactly 15.2(4)e3
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Verify TCP processing is enabledThis vulnerability is triggered by receiving crafted TCP packets on any interface. By default, TCP processing is enabled on Cisco IOS interfaces for management and control plane traffic. No special feature needs to be explicitly enabled.Affected if The device has IP addresses configured on interfaces and can receive TCP traffic (standard operating condition)
The device is affected only if it is a Cisco Catalyst 4000 Series Switch running exactly Cisco IOS version 15.2(3)e1 or 15.2(4)e3 and can receive TCP packets from the network.
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 appropriate Cisco IOS software update/patch for the Catalyst 4000 Series Switches as provided in the Cisco security advisory. Until patched, consider implementing access control lists (ACLs) on management interfaces to limit TCP traffic from untrusted sources.
Fix this in iOS
Scoped from the published advisory
- Consultation4.0 h
- Implementation4.0 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-2019-12652 — 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-2019-12652 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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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.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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