iOSOperating system · Cisco
CVE-2015-6429
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 IKEv1 state machine in Cisco IOS 15.4 through 15.6 and IOS XE 3.15 through 3.17 allows remote attackers to cause a denial of service (IPsec connection termination) via a crafted IKEv1 packet to a tunnel endpoint, aka Bug ID CSCuw08236.
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 · moderate confidenceThe IKEv1 state machine in Cisco IOS 15.4-15.6 and IOS XE 3.15-3.17 contains a flaw in processing specially crafted IKEv1 packets. When a remote attacker sends a malformed IKEv1 packet to an IPsec VPN tunnel endpoint, it causes the state machine to enter an error condition, resulting in termination of the IPsec connection (denial of service).
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\(3\)s= 15.5\(1\)s= 15.5\(1\)t= 15.5\(2\)s= 15.5\(2\)t= 15.5\(3\)m= 15.5\(3\)m1= 15.5\(3\)s= 15.5\(3\)s1= 15.6\(0.17\)t= 15.6\(1\)t0a
Ios XeOperating system
= 3.15s.0= 3.15s.1= 3.15s.2= 3.16s.0= 3.16s.1= 3.17s.0= 3.17s.1CVSS 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
- Partial
AV:N/AC:L/Au:N/C:N/I:N/A:P
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 or IOS XE versionRun 'show version' on the device CLI and note the exact firmware version string (for example, 15.5(3)s or 3.16s.0)Affected if The installed version matches one of the affected versions listed in the CVE (15.4(3)s, 15.5(1)s through 15.6(1)t0a for IOS, or 3.15s.0 through 3.17s.1 for IOS XE)
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Verify IPsec VPN is configuredRun 'show crypto ipsec sa' to check for active IPsec security associations, or 'show crypto isakmp sa' to check IKE security associationsAffected if Any IPsec VPN tunnels are active on the device
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Confirm IKEv1 is in use for VPN tunnelsRun 'show crypto isakmp sa detail' and examine the IKE version column; also check crypto maps with 'show crypto map' to see which IKE version is specifiedAffected if Any tunnel is using IKEv1 (version 1) rather than IKEv2
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Check for IKEv1 processing of remote trafficReview 'show crypto isakmp stats' or interface IKE counters to confirm the device processes IKEv1 packets from remote peers on UDP port 500Affected if The device accepts and processes IKEv1 packets from remote VPN peers
The device is affected if it runs a matching IOS/IOS XE version, has IPsec VPN configured, and uses IKEv1 for tunnel establishment.
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 Cisco IOS/IOS XE patches for Bug ID CSCuw08236 to upgrade to a fixed version. As an interim measure, consider filtering IKEv1 traffic (UDP port 500) at the network perimeter from untrusted sources or migrating to IKEv2 which may not be affected by this specific state machine flaw.
Fix this in iOS
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 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 $5,120.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2015-6429 — 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-2015-6429 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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- Version or environment caveats, and links to real fixes
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