iOSOperating system · Cisco
CVE-2013-6693
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 MLDP implementation in Cisco IOS 15.3(3)S and earlier on 7600 routers, when many VRFs are configured, allows remote attackers to cause a denial of service (chunk corruption and device reload) by establishing many multicast flows, aka Bug ID CSCue22345.
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 MLDP (Multicast Label Distribution Protocol) implementation in Cisco IOS 15.3(3)S and earlier on 7600 routers contains a memory corruption vulnerability triggered when many VRFs are configured and an attacker establishes numerous multicast flows. This causes chunk corruption leading to forced device reload, resulting in 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
<= 15.3\(3\)s= 15.3\(2\)s= 15.3s
7600 RouterHardware / appliance
all versionsCVSS 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
- High
- Authentication
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- Complete
AV:N/AC:H/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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Check Cisco IOS versionExecute 'show version' on the router CLI and locate the IOS release string (e.g., 15.3(3)S, 15.3(2)S). Compare this version against the affected range: any 15.3s version <= 15.3(3)S. Also confirm the hardware is a Cisco 7600 series router via the same output.Affected if The router runs Cisco IOS 15.3(3)S or earlier on a 7600 platform.
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Verify MLDP is enabledExecute 'show mldp' or 'show ip mldp' to display MLDP (Multicast Label Distribution Protocol) status. Look for output indicating MLDP is enabled or active.Affected if MLDP is currently enabled or operational on the device.
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Count configured VRFsExecute 'show vrf' to list all VRFs (Virtual Routing and Forwarding instances) configured on the router. Count the total number displayed.Affected if A high number of VRFs are configured (the vulnerability triggers when 'many' VRFs exist).
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Inspect active multicast flowsExecute 'show ip mroute' to display multicast routing table entries. Look for an unusually high number of active multicast flows or sources, which may indicate an ongoing attack.Affected if There is a sudden or abnormally high volume of multicast flows active on the router.
The device is affected if it is a Cisco 7600 router running IOS 15.3(3)S or earlier, MLDP is enabled, and many VRFs are configured, combined with numerous active multicast flows potentially from an attacker.
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 fixed Cisco IOS version. If immediate patching is not feasible, limit the number of VRFs with MLDP enabled or restrict multicast flow establishment through access controls until the IOS update can be applied.
Fix this in iOS
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 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 $5,600.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2013-6693 — 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-2013-6693 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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