iOSOperating system · Cisco
CVE-2013-6686
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 SSL VPN implementation in Cisco IOS 15.3(1)T2 and earlier allows remote authenticated users to cause a denial of service (interface queue wedge) via crafted DTLS packets in an SSL session, aka Bug IDs CSCuh97409 and CSCud90568.
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 confidenceCisco IOS SSL VPN implementation before version 15.3(1)T2 contains a vulnerability where crafted DTLS packets within an SSL VPN session can cause the interface queue to wedge (become stuck), resulting in denial of service. The attack requires authenticated remote users with valid SSL VPN credentials.
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
<= 15.3= 15.0= 15.0\(1\)se= 15.1= 15.2CVSS 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
- Single
- Confidentiality
- None
- Integrity
- None
- Availability
- Complete
AV:N/AC:L/Au:S/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' on the device console or via remote access. Locate the IOS release number (for example, 15.2(4)E, 15.3(1)T1).Affected if The version falls within 15.0, 15.0(1)se, 15.1, 15.2, or any 15.3 version earlier than 15.3(1)T2
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Check if SSL VPN is configured or enabledRun 'show running-config | include webvpn' or 'show vpn-sessiondb summary' to see if WebVPN or AnyConnect SSL VPN is configured. Also check for ssl vpn gateway or webvpn context in the configuration.Affected if SSL VPN (WebVPN, AnyConnect) is configured or has been active on the device
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Confirm DTLS is in use for SSL VPNReview the SSL VPN configuration with 'show running-config | include dtls' or inspect the WebVPN/AnyConnect tunnel group settings for DTLS parameter settings.Affected if DTLS is enabled within the SSL VPN configuration (DTLS is the default transport for AnyConnect and some WebVPN deployments)
Device is affected if running a vulnerable IOS version listed above AND has SSL VPN with DTLS enabled, since the crafted DTLS packets require an active SSL VPN session to trigger the queue wedge.
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 Cisco IOS to version 15.3(1)T2 or later. If immediate upgrade is not feasible, consider restricting SSL VPN access to trusted user populations and monitoring for unusual DTLS traffic patterns.
Fix this in iOS
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2013-6686 — 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-2013-6686 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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