CVE-1999-1085
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 · uneditedSSH 1.2.25, 1.2.23, and other versions, when used in in CBC (Cipher Block Chaining) or CFB (Cipher Feedback 64 bits) modes, allows remote attackers to insert arbitrary data into an existing stream between an SSH client and server by using a known plaintext attack and computing a valid CRC-32 checksum for the packet, aka the "SSH insertion attack."
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 confidenceSSH1 protocol implementation allows remote attackers to inject arbitrary data into encrypted sessions when using CBC or CFB (64-bit) cipher modes. Attackers exploit a known plaintext weakness combined with CRC-32 checksum manipulation to insert malicious content into the SSH stream between client and server.
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= 1.2.23= 1.2.25CVSS 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
- Partial
- Availability
- None
AV:N/AC:L/Au:N/C:N/I:P/A:N
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 SSH versionRun 'ssh -V' or 'ssh -v' to display version information, or check the binary file metadata for the SSH client/server softwareAffected if Version displayed is 1.2.23 or 1.2.25
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Verify SSH protocol version 1 is enabledCheck SSH configuration files (typically /etc/ssh/sshd_config or ~/.ssh/config) for 'Protocol 1' or 'Protocol 2' directives; if 'Protocol 1' is present or if no Protocol directive exists (defaulting to both), SSH1 may be activeAffected if Protocol 1 is explicitly enabled or the configuration allows protocol version 1 connections
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Inspect enabled cipher modesReview SSH configuration for Ciphers directive - look for cbc (CBC mode) or cfb (CFB mode) cipher listings such as aes128-cbc, 3des-cbc, or other CBC/CFB variantsAffected if CBC or CFB mode ciphers are listed in the cipher configuration and SSH1 protocol is in use
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Confirm active SSH1 daemon or clientCheck running processes for sshd version 1 daemons or examine network listening services on port 22 for SSH1 banner responses using 'nc -v server 22' to observe the greetingAffected if SSH1 daemon is running or the server responds with SSH-1.x banner indicating protocol version 1 support
Environment is affected if SSH version is 1.2.23 or 1.2.25, SSH protocol version 1 is enabled, and CBC or CFB cipher modes are configured for SSH1 connections.
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 dataDisable SSH protocol version 1 entirely on all servers and clients, or upgrade to SSH2 which is not vulnerable to this insertion attack. If SSH1 must be retained for legacy reasons, disable CBC and CFB cipher modes.
- Consultation1.0 h
- Implementation2.0 h
- Testing1.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-1999-1085 — 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-1999-1085 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
- No weaponised exploit code, or anything meant to cause harm
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