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iOSOperating system · Cisco

CVE-2012-3893

MEDIUM · 6.3 CVSS v2.0 Published 2012-09-16
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
69/100
Remediation priority · Elevated
Remotely reachable Zero-click

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 · unedited
The FlexVPN implementation in Cisco IOS 15.2 and 15.3 allows remote authenticated users to cause a denial of service (spoke crash) via spoke-to-spoke traffic, aka Bug ID CSCtz02622.

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 confidence

A denial of service vulnerability exists in Cisco IOS FlexVPN implementations versions 15.2 and 15.3. Remote authenticated users can trigger a spoke crash by sending spoke-to-spoke traffic through the FlexVPN tunnel, causing the affected spoke device to become unavailable.

MitigationUpgrade Cisco IOS to a version beyond 15.3 that contains the fix for Bug ID CSCtz02622. If immediate upgrade is not feasible, restrict VPN user access and monitor for DoS conditions on FlexVPN spokes.

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
Affected:= 15.2= 15.3

CVSS 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
M
Authentication
Single
Confidentiality
None
Integrity
None
Availability
Complete

AV:N/AC:M/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify Cisco IOS version
    Run 'show version' command and locate the IOS version number in the output
    Affected if The version displayed is 15.2 or 15.3
  2. Verify FlexVPN is configured
    Run 'show crypto session' or 'show ipsec sa' and look for FlexVPN-related tunnel interfaces
    Affected if FlexVPN tunnels or crypto sessions are active
  3. Confirm spoke role in FlexVPN topology
    Run 'show crypto isakmp sa' to identify if the device is acting as a spoke in a hub-and-spoke configuration
    Affected if Device is configured as a FlexVPN spoke with active IKE Security Associations to a hub

A system is affected if it runs Cisco IOS version 15.2 or 15.3 with FlexVPN enabled and configured as a spoke in the topology

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Cisco IOS to a version beyond 15.3 that contains the fix for Bug ID CSCtz02622. If immediate upgrade is not feasible, restrict VPN user access and monitor for DoS conditions on FlexVPN spokes.

Fix this in iOS Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2012-3893 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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