FedoraOperating system · Fedoraproject
CVE-2023-1667
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 · uneditedA NULL pointer dereference was found In libssh during re-keying with algorithm guessing. This issue may allow an authenticated client to cause a denial of service.
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 confidenceA NULL pointer dereference vulnerability exists in libssh during the re-keying handshake when the server attempts to guess the client's preferred algorithm. An authenticated client can trigger this condition during algorithm negotiation, causing the server to crash due to dereferencing a NULL pointer.
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
FedoraOperating system
= 37
Debian LinuxOperating system
= 10.0
Enterprise LinuxOperating system
= 8.0= 9.0>= 0.9.1, <= 0.9.6>= 0.10.0, <= 0.10.4CVSS 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
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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 versionRun 'rpm -q libssh' on RHEL/Fedora or 'dpkg -l libssh' on Debian to retrieve the installed package versionAffected if The version falls within 0.9.1 to 0.9.6, or 0.10.0 to 0.10.4
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Confirm libssh is in use as an SSH serverCheck if the sshd service is running ('systemctl status sshd' or 'ps aux | grep sshd') and linked against libsshAffected if sshd is active and depends on libssh libraries, which is typical for many SSH server implementations
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Verify algorithm negotiation is enabledReview SSH server configuration for default or explicit algorithm negotiation settings in /etc/ssh/sshd_configAffected if Default algorithm negotiation is enabled (this is the default behavior in standard OpenSSH configurations using libssh)
If the installed libssh version is 0.9.1-0.9.6 or 0.10.0-0.10.4 and the system runs an SSH server that uses libssh, the server is vulnerable to crashes during re-keying handshake with authenticated clients.
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.
dbcve · scopedUpgrade libssh to the patched version that addresses this NULL pointer dereference in the re-keying algorithm guessing code path.
libssh 0.9.7 or later / libssh 0.10.5 or later
- 1. Identify the currently installed libssh version using your package manager (e.g., `rpm -q libssh` or `dpkg -l libssh`)
- 2. For systems running libssh 0.9.x: upgrade to libssh version 0.9.7 or later
- 3. For systems running libssh 0.10.x: upgrade to libssh version 0.10.5 or later
- 4. Verify the upgrade was successful by checking the new version
- 5. Restart any services that depend on libssh to ensure the patched library is loaded
- 6. Test SSH functionality to confirm the service operates normally after the update
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Fedora
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-1667 — 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-2023-1667 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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