Enterprise LinuxOperating system · Redhat
CVE-2009-1893
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 configtest function in the Red Hat dhcpd init script for DHCP 3.0.1 in Red Hat Enterprise Linux (RHEL) 3 allows local users to overwrite arbitrary files via a symlink attack on an unspecified temporary file, related to the "dhcpd -t" command.
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 confidenceThe dhcpd init script's configtest function creates a temporary file without proper safety measures when executing 'dhcpd -t' for configuration validation. A local attacker can exploit this by creating a symlink at the predictable temporary file location, causing the init script to overwrite arbitrary files owned by the user running the dhcpd command (typically root).
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
Enterprise LinuxOperating system
= 3.0= 3.0.1CVSS 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
- 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 dhcpd package versionRun 'rpm -q dhcp' or check the installed dhcpd package version using your system's package managerAffected if The installed version matches 3.0.1 for ISC DHCP or the system is Red Hat Enterprise Linux 3.0
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Locate the dhcpd init scriptFind the dhcpd init script in your system (commonly in /etc/init.d/ or /etc/rc.d/init.d/) using 'find /etc -name dhcpd' or similarAffected if An init script exists and contains a configtest function that runs 'dhcpd -t' for configuration validation
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Examine the configtest function for temporary file handlingOpen the dhcpd init script and locate the configtest function. Search for any temporary file creation during the 'dhcpd -t' executionAffected if The configtest function creates a temporary file without using mktemp or O_EXCL flag for safe atomic file creation
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Check for predictable temporary file pathsReview the init script for hardcoded or predictable temporary file paths (such as /tmp/dhcpd-test or similar) used during config validationAffected if The script uses a predictable temporary file path that could be pre-created by a local attacker as a symlink
Your environment is affected if you are running the vulnerable dhcpd version on RHEL 3.0 or ISC DHCP 3.0.1 and the init script's configtest function performs insecure temporary file operations when validating the configuration.
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 dataReplace the insecure temporary file handling in the dhcpd init script's configtest function with safe practices such as using mktemp or O_EXCL flag for atomic file creation, and ensure proper file permissions on any temporary files created during the configtest operation.
Fix this in Enterprise Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2009-1893 — 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-2009-1893 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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