iOSOperating system · Cisco
CVE-2016-6423
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 IKEv2 client and initiator implementations in Cisco IOS 15.5(3)M and IOS XE allow remote IKEv2 servers to cause a denial of service (device reload) via crafted IKEv2 packets, aka Bug ID CSCux97540.
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 exists in the IKEv2 client and initiator implementations of Cisco IOS 15.5(3)M and IOS XE where specially crafted IKEv2 packets sent by a remote IKEv2 server can trigger a denial of service condition causing the device to reload.
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
= 15.5\(3\)mCVSS 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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.0/AV:N/AC:L/PR:L/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.
-
Identify the Cisco IOS versionRun 'show version' and look for the version string in the output. It should display as something like '15.5(3)M' or similar.Affected if The version displayed is exactly 15.5(3)M or falls within the 15.5(3)M branch (15.5(3)m, 15.5(3)M, etc.)
-
Confirm the platform runs Cisco IOSThe 'show version' output will indicate if the device is running Cisco IOS (not IOS XE).Affected if The device is running Cisco IOS and the version matches 15.5(3)M
-
Verify IKEv2 is configuredRun 'show crypto ikev2 session' or 'show crypto isakmp sa' to check for active IKEv2 security associations. Also run 'show running-config | include ikev2' to see if IKEv2 is enabled in the configuration.Affected if IKEv2 is actively configured or has active sessions on the device
-
Check if device acts as IKEv2 client or initiatorReview the IKEv2 configuration for any 'crypto ikev2' entries that configure the device as a client or initiator connecting to remote IKEv2 servers.Affected if The device is configured as an IKEv2 client or initiator that initiates connections to remote IKEv2 servers
A device is affected if it runs Cisco IOS version 15.5(3)M, has IKEv2 enabled, and is configured as an IKEv2 client or initiator.
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 patch for bug CSCux97540 or upgrade to a Cisco IOS version beyond 15.5(3)M that contains the fix. As a temporary workaround, consider restricting IKEv2 traffic with ACLs to only trusted peer IP addresses.
Fix this in iOS
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-6423 — 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-2016-6423 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data