Debian LinuxOperating system · Debian
CVE-2012-0920
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 · uneditedUse-after-free vulnerability in Dropbear SSH Server 0.52 through 2012.54, when command restriction and public key authentication are enabled, allows remote authenticated users to execute arbitrary code and bypass command restrictions via multiple crafted command requests, related to "channels concurrency."
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 confidenceDropbear SSH Server versions 0.52 through 2012.54 contain a use-after-free vulnerability in channel concurrency handling. When both command restriction and public key authentication are enabled, an authenticated remote attacker can send multiple crafted command requests to trigger the use-after-free, achieving arbitrary code execution and bypassing configured command restrictions.
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
Debian LinuxOperating system
= 6.0= 7.0>= 0.52, <= 2012.54CVSS 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
- Single
- Confidentiality
- Complete
- Integrity
- Complete
- Availability
- Complete
AV:N/AC:H/Au:S/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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Check installed Dropbear versionRun 'dropbear -V' or 'dropbear -v' to display version information, or use 'dpkg -l | grep dropbear' on Debian systemsAffected if Version number is 0.52 through 2012.54 (inclusive)
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Verify public key authentication is enabledCheck for the presence of authorized_keys files in user .ssh directories (ls -la ~/.ssh/authorized_keys) or examine Dropbear configuration files for PubkeyAuth or similar settingsAffected if Public key authentication is configured and authorized_keys files exist or are permitted
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Identify if command restrictions are configuredSearch authorized_keys files for 'command=' restrictions (grep -r 'command=' ~/.ssh/authorized_keys or in /root/.ssh/authorized_keys)Affected if Any user has a 'command=' restriction specified in their authorized_keys file
User is affected if Dropbear version is between 0.52 and 2012.54 AND both public key authentication and command restrictions are simultaneously enabled in their configuration.
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 Dropbear SSH Server to a version beyond 2012.54 that contains the patched channel concurrency handling. If immediate upgrade is not possible, consider disabling public key authentication or command restrictions as a temporary workaround, though this significantly impacts server functionality.
Fix this in Debian Linux
Scoped from the published advisory
- Consultation3.0 h
- Implementation6.0 h
- Testing4.0 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 $4,224.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2012-0920 — 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-2012-0920 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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