CVE-2009-2904
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 certain Red Hat modification to the ChrootDirectory feature in OpenSSH 4.8, as used in sshd in OpenSSH 4.3 in Red Hat Enterprise Linux (RHEL) 5.4 and Fedora 11, allows local users to gain privileges via hard links to setuid programs that use configuration files within the chroot directory, related to requirements for directory ownership.
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 vulnerability in Red Hat's modification to OpenSSH's ChrootDirectory feature allows local users to escalate privileges by creating hard links to setuid programs that use configuration files within the chroot directory. The flaw stems from insufficient validation of directory ownership requirements when the chroot environment is established, enabling attackers to manipulate setuid binaries through hard-linked configuration files to gain elevated privileges.
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= 4.3= 4.8CVSS 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
- Local
- Complexity
- M
- Authentication
- None
- Confidentiality
- Complete
- Integrity
- Complete
- Availability
- Complete
AV:L/AC:M/Au:N/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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Identify installed OpenSSH versionRun 'ssh -V' or check the package manager (e.g., 'rpm -q openssh' on RHEL, 'dpkg -l openssh-server' on Debian)Affected if The version matches OpenSSH 4.3 or 4.8 (or falls within an unpatched range based on these versions)
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Determine if ChrootDirectory is configuredReview OpenSSH server configuration file (typically /etc/ssh/sshd_config) for any 'ChrootDirectory' directivesAffected if ChrootDirectory is actively configured and in use for any user or group
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Inspect ownership of chroot directoriesExamine the ownership of directories specified in ChrootDirectory directives. Use 'ls -ld <chroot_path>' to check if root (uid 0) owns the parent directoryAffected if Any chroot directory is not owned by root or has permissive permissions allowing untrusted users to create hard links
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Search for setuid binaries within chroot environmentsFind setuid programs inside chroot directories using 'find <chroot_dir> -perm -4000 -type f' as rootAffected if Setuid binaries exist within directories that untrusted users can access or modify
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Detect hard links to setuid binariesUse 'find / -type f -links +1' combined with permission checks, or specifically examine the chroot directories for hard links pointing to setuid binaries from writable locationsAffected if Hard links to setuid binaries exist and can be manipulated by untrusted users through configuration file access
A user is affected if they run an unpatched OpenSSH version (4.3 or 4.8) with ChrootDirectory configured, where the chroot environment contains setuid binaries and untrusted users can create hard links to those binaries from writable directories.
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 to patched versions of OpenSSH (RHEL 5.4 and Fedora 11 received updates), and ensure proper directory ownership and permissions within chroot environments—specifically, ensure no hard links exist to setuid programs from directories writable by untrusted users.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2009-2904 — 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-2009-2904 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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