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iOSOperating system · Cisco

CVE-2012-0386

HIGH · 7.8 CVSS v2.0 Published 2012-03-29
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
87/100
Remediation priority · High
Remotely reachable No privileges 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 SSHv2 implementation in Cisco IOS 12.2, 12.4, 15.0, 15.1, and 15.2 and IOS XE 2.3.x through 2.6.x and 3.1.xS through 3.4.xS before 3.4.2S allows remote attackers to cause a denial of service (device reload) via a crafted username in a reverse SSH login attempt, aka Bug ID CSCtr49064.

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 confidence

A vulnerability in the SSHv2 implementation in Cisco IOS and IOS XE allows remote attackers to cause a denial of service (device reload) by sending a crafted username during a reverse SSH login attempt. The issue affects specific versions of IOS 12.2, 12.4, 15.0-15.2 and IOS XE 2.3.x-2.6.x and 3.1.xS-3.4.xS before 3.4.2S.

MitigationUpgrade Cisco IOS or IOS XE to a patched version (IOS XE 3.4.2S or later) or apply vendor-supplied patches. If immediate patching is not possible, consider restricting SSH access through ACLs or disabling reverse SSH until the upgrade can be performed.

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:= 12.2= 12.4= 15.0= 15.1= 15.2
Ios XeOperating system
Affected:= 2.3= 2.3.0= 2.3.1= 2.3.1t= 2.3.2= 2.4= 2.4.0= 2.4.1= 2.4.2= 2.4.3= 2.4.4= 2.5.0

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
Low
Authentication
None
Confidentiality
None
Integrity
None
Availability
Complete

AV:N/AC:L/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 checks

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

  1. Check Cisco IOS/IOS XE version
    Execute 'show version' on the device and locate the software version line (e.g., 'Cisco IOS Software, ... Version 15.2(4)E').
    Affected if The version falls within 12.2, 12.4, 15.0, 15.1, 15.2 for IOS, or 2.3.x-2.6.x or 3.1.xS-3.4.xS for IOS XE (prior to 3.4.2S).
  2. Determine if reverse SSH is enabled
    Execute 'show running-config | include reverse-ssh' or review the configuration for any 'reverse-ssh' entries under the SSH configuration section.
    Affected if Reverse SSH is actively configured on the device.
  3. Verify SSH service status
    Execute 'show ip ssh' or 'show ssh' to confirm SSHv2 is enabled and note the configuration settings.
    Affected if SSH service is running (the vulnerability only affects SSHv2 implementation).

The device is affected if it runs a vulnerable IOS/IOS XE version (12.2, 12.4, 15.0-15.2 or IOS XE 2.3.x-2.6.x/3.1.xS-3.4.xS before 3.4.2S) AND has reverse SSH functionality enabled.

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 or IOS XE to a patched version (IOS XE 3.4.2S or later) or apply vendor-supplied patches. If immediate patching is not possible, consider restricting SSH access through ACLs or disabling reverse SSH until the upgrade can be performed.

Fix this in iOS Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,330
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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-2012-0386 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