iOSOperating system · Cisco
CVE-2015-6366
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 · uneditedCisco IOS 15.2(04)M6 and 15.4(03)S lets physical-interface ACLs supersede tunnel-interface ACLs, which allows remote attackers to bypass intended network-traffic restrictions in opportunistic circumstances by using a tunnel, aka Bug ID CSCur01042.
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 confidenceThis Cisco IOS vulnerability allows physical interface ACLs to incorrectly take precedence over tunnel interface ACLs. Attackers can exploit this by routing traffic through tunnels where the physical interface has a less restrictive ACL, bypassing intended tunnel-based access controls. The issue affects specific IOS versions 15.2(04)M6 and 15.4(03)S.
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
= 15.2\(4\)m6= 15.4\(3\)sCVSS 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
- Partial
- Availability
- None
AV:N/AC:L/Au:N/C:N/I:P/A:N
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' command and locate the 'IOS' or 'Cisco IOS Software' line in the outputAffected if The version displayed matches exactly 15.2(4)M6 or 15.4(3)S
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Determine if tunnel interfaces existRun 'show interface tunnel brief' or 'show ip interface brief' and look for Tunnel interfaces in the outputAffected if Any tunnel interfaces are configured and active
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Identify ACLs applied to tunnel interfacesRun 'show running-config interface <tunnel-number>' for each tunnel interface to see if 'ip access-group' or 'access-group' commands are presentAffected if Tunnel interfaces have ACLs configured via 'ip access-group'
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Identify ACLs applied to underlying physical interfacesRun 'show running-config interface <physical-interface>' for each physical interface that could carry tunnel traffic, checking for 'ip access-group' commandsAffected if Physical interfaces carrying tunnel traffic have ACLs configured
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Compare physical and tunnel interface ACL restrictionsRun 'show access-lists' to display the ACL entries, then compare the permit/deny rules on the physical interface versus the tunnel interface for the same traffic flowsAffected if The physical interface ACL is less restrictive (permits more traffic) than the tunnel interface ACL for the same source/destination patterns
You are affected only if your device runs IOS version 15.2(4)M6 or 15.4(3)S AND has both tunnel and physical interfaces with ACLs where the physical interface ACL permits traffic that the tunnel ACL would deny.
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 dataReview and ensure ACLs are properly configured on both physical and tunnel interfaces to enforce intended restrictions. Consider upgrading to patched IOS versions if available, or implement additional controls such as zone-based firewalls.
Fix this in iOS
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 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-2015-6366 — 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-2015-6366 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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