iOSOperating system · Cisco
CVE-2011-0935
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 PKI functionality in Cisco IOS 15.0 and 15.1 does not prevent permanent caching of certain public keys, which allows remote attackers to bypass authentication and have unspecified other impact by leveraging an IKE peer relationship in which a key was previously valid but later revoked, aka Bug ID CSCth82164, a different vulnerability than CVE-2010-4685.
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 PKI functionality in Cisco IOS 15.0 and 15.1 does not prevent permanent caching of certain public keys. This allows remote attackers to bypass authentication by leveraging an IKE peer relationship where a key was previously valid but later revoked, leading to unauthorized access.
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
= 15.0= 15.1CVSS 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
- Complete
- Integrity
- Complete
- Availability
- Complete
AV:N/AC:L/Au:N/C:C/I:C/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 versionExecute 'show version' on the device CLI and locate the IOS version number in the outputAffected if The version displayed is exactly 15.0 or 15.1 (e.g., 15.0(1)T, 15.1(1)T, etc.)
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Verify PKI functionality is in useExecute 'show crypto pki certificate' or 'show crypto pki trustpoints' to check if PKI certificates are configuredAffected if PKI trustpoints or certificates are configured and active on the device
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Confirm IKEv1 or IKEv2 peer configurations existExecute 'show crypto isakmp sa' or 'show crypto ipsec sa' to list active IKE Security Associations, or review the configuration with 'show running-config | include isakmp'
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Inspect certificate revocation checking configurationCheck the PKI trustpoint configuration with 'show crypto pki trustpoint <name>' and look for 'revocation-check' settings in the running-config under the crypto pki trustpoint sectionAffected if The 'revocation-check' is set to 'none' or is explicitly disabled, allowing cached keys to remain valid despite revocation
A device is affected if it runs Cisco IOS version 15.0 or 15.1, has PKI certificates configured, uses IKE peers for VPN or tunnel authentication, and does not enforce certificate revocation checking, allowing previously valid but later revoked keys to remain usable for authentication.
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 a version that addresses this vulnerability. Review and ensure proper public key revocation checking is enforced in IKE peer configurations.
Fix this in iOS
Scoped from the published advisory
- Consultation6.0 h
- Implementation12.0 h
- Testing6.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,968.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2011-0935 — 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-2011-0935 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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