CVE-2004-1653
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 default configuration for OpenSSH enables AllowTcpForwarding, which could allow remote authenticated users to perform a port bounce, when configured with an anonymous access program such as AnonCVS.
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 confidenceOpenSSH's default configuration enables AllowTcpForwarding, which allows any remote authenticated user to use the SSH server as a TCP proxy for port bouncing. This enables attackers to relay connections through the compromised SSH server to bypass network restrictions or obfuscate their origin, particularly dangerous when combined with anonymous access services.
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<= 3.9CVSS 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
- Partial
- Integrity
- Partial
- Availability
- None
AV:N/AC:L/Au:N/C:P/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.
-
Check installed OpenSSH versionRun 'sshd -v' or 'sshd -V' to display version information, or check your package manager (e.g., 'dpkg -l openssh-server' on Debian/Ubuntu, 'rpm -q openssh-server' on RHEL/CentOS)Affected if The installed version is 3.9 or earlier
-
Locate sshd configuration fileThe default path is /etc/ssh/sshd_config. Verify this file exists and is readable by running 'ls -la /etc/ssh/sshd_config'Affected if The configuration file cannot be found at the default location
-
Inspect AllowTcpForwarding settingRun 'grep -i "AllowTcpForwarding" /etc/ssh/sshd_config' to see if the directive is present. If commented out or missing, OpenSSH defaults to 'yes' (enabled)Affected if The directive is set to 'yes', is commented with a '#', or is absent entirely (defaulting to enabled)
-
Verify TCP forwarding is actually functionalAs a test, attempt to establish a local TCP forward through the SSH server using 'ssh -L <local_port>:<target>:<target_port> user@localhost' - if connection succeeds, forwarding is activeAffected if The SSH connection with local port forwarding completes successfully, confirming TCP forwarding is enabled
You are affected if your OpenSSH version is 3.9 or earlier AND AllowTcpForwarding is not explicitly set to 'no' in your sshd_config (or is set to 'yes').
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 AllowTcpForwarding in /etc/ssh/sshd_config by setting it to 'no' and restart the sshd service. Verify that legitimate applications do not require TCP forwarding before applying.
- Consultation2.0 h
- Implementation1.0 h
- Testing2.0 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 $1,696.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2004-1653 — 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-2004-1653 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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.
- 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