iOSOperating system · Cisco
CVE-2015-0592
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 · uneditedThe Zone-Based Firewall implementation in Cisco IOS 15.4(2)T3 and earlier allows remote attackers to cause a denial of service (device reload) via crafted network traffic that triggers incorrect kernel-timer handling, aka Bug ID CSCuh25672.
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 confidenceThe Zone-Based Firewall in Cisco IOS 15.4(2)T3 and earlier contains a kernel-timer handling flaw triggered by specially crafted network traffic. Remote attackers can exploit this to cause the device to reload, resulting in denial of service. The vulnerability stems from incorrect timer management when processing specific firewall traffic patterns.
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
<= 15.4\(2\)t3= 15.4\(1\)t= 15.4\(1\)t1= 15.4\(1\)t2= 15.4\(1\)t3= 15.4\(1\)t4= 15.4\(2\)t= 15.4\(2\)t1= 15.4\(2\)t2= 15.4tCVSS 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
- Authentication
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- Complete
AV:N/AC:L/Au:N/C:N/I:N/A:C
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 Cisco IOS versionRun 'show version' or 'show version | include Version' to display the installed IOS versionAffected if The version displayed is 15.4(2)T3 or earlier, or matches one of the listed affected versions: 15.4(1)t, 15.4(1)t1, 15.4(1)t2, 15.4(1)t3, 15.4(1)t4, 15.4(2)t, 15.4(2)t1, 15.4(2)t2, or 15.4t (case-insensitive)
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Verify Zone-Based Firewall is configuredRun 'show zone-pair security' to list configured zone pairs, and 'show running-config | include class-map|type zone' to identify ZBF policy configurationsAffected if Any zone pairs or ZBF policy maps are present, indicating ZBF is actively configured on the device
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Confirm ZBF is actively enforcing policiesRun 'show zone-pair security' and check the 'Status' field; also run 'show policy-map type zone-pair' to view active policy configurationsAffected if The zone-pair status shows as 'Active' or any ZBF policy-map exists with inspection rules configured
The device is affected if it runs Cisco IOS version 15.4(2)T3 or earlier (including the specific versions listed) AND has Zone-Based Firewall with active policies configured, making it vulnerable to remote reload via specially crafted traffic patterns.
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 dataUpgrade to a patched Cisco IOS version beyond 15.4(2)T3. If immediate patching is not feasible, restrict remote access to the firewall interface using ACLs or isolate the device behind additional network controls to reduce exposure to untrusted traffic.
Fix this in iOS
Scoped from the published advisory
- Consultation4.0 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-2015-0592 — 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-2015-0592 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
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