CVE-2012-4561
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 (1) publickey_make_dss, (2) publickey_make_rsa, (3) signature_from_string, (4) ssh_do_sign, and (5) ssh_sign_session_id functions in keys.c in libssh before 0.5.3 free "an invalid pointer on an error path," which might allow remote attackers to cause a denial of service (crash) via unspecified vectors.
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 confidenceThis is a double-free vulnerability in libssh versions before 0.5.3 where multiple key handling functions (publickey_make_dss, publickey_make_rsa, signature_from_string, ssh_do_sign, ssh_sign_session_id) in keys.c incorrectly free an invalid pointer on error paths, potentially causing a crash via a use-after-free or double-free condition.
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<= 0.5.2= 0.4.7= 0.4.8= 0.5.0= 0.5.1CVSS 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
- None
- Integrity
- None
- Availability
- Partial
AV:N/AC:L/Au:N/C:N/I:N/A:P
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 installed libssh library versionRun 'ssh -V' or check your application's linked libraries using 'ldd' or 'dpkg -l | grep libssh' on Linux, or check the binary properties on WindowsAffected if The reported version is 0.4.7, 0.4.8, 0.5.0, 0.5.1, or any version <= 0.5.2
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Locate libssh shared libraryFind the libssh shared library file (libssh.so on Linux, libssh.dll on Windows) in your system paths or application directoryAffected if The library file exists and its version cannot be confirmed as 0.5.3 or later
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Inspect keys.c source file if availableIf you have access to the libssh source code in use, examine the files keys.c and check the error handling paths in functions: publickey_make_dss, publickey_make_rsa, signature_from_string, ssh_do_sign, ssh_sign_session_idAffected if The code shows missing NULL pointer validation before free() calls in error paths of these functions (vulnerable code pattern)
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Check application logs for crashesReview application and system logs for crashes, memory corruption errors, or segfaults occurring during SSH key operations, particularly during authentication or public key handlingAffected if Crashes occur during SSH public key operations and the libssh version is within the affected range
You are affected if your installed libssh library version is 0.4.7, 0.4.8, 0.5.0, 0.5.1, or any version 0.5.2 or lower.
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 libssh to version 0.5.3 or later. If upgrade is not possible, apply vendor patches that fix the error path handling in keys.c to ensure pointers are validated or NULL-checked before being freed.
- Consultation3.0 h
- Implementation6.0 h
- Testing4.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2012-4561 — 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-2012-4561 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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