Linux KernelOperating system · Linux
CVE-2006-1624
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 of syslogd in the Linux sysklogd package does not enable the -x (disable name lookups) option, which allows remote attackers to cause a denial of service (traffic amplification) via messages with spoofed source IP addresses.
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 sysklogd package's syslogd daemon, by default, performs reverse DNS lookups on source IP addresses from incoming syslog messages. Attackers can exploit this by sending syslog messages with spoofed source IP addresses (e.g., victim's IP), causing the daemon to attempt DNS resolution on those addresses. This consumes server resources (CPU, memory) and can amplify traffic, leading to denial of service.
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
Linux KernelOperating system
= 2.6.20.1CVSS 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
- Network
- Complexity
- Low
- Authentication
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- Complete
AV:N/AC:L/Au:N/C:N/I:N/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 if syslogd is runningRun 'ps aux | grep syslogd' to find running syslogd processes. Also check 'netstat -an | grep 514' or 'ss -an | grep 514' to see if syslog is listening on port 514/UDP for remote messages.Affected if syslogd is running and accepting remote syslog messages (listening on UDP port 514)
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Locate syslogd startup configurationCheck common syslogd config locations: /etc/sysconfig/syslog (RHEL/CentOS), /etc/default/syslogd (Debian/Ubuntu), or /etc/init.d/syslog startup scripts. Look for the SYSLOGD_OPTIONS or similar variable.Affected if The configuration file exists and shows syslogd startup options without the -x flag
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Verify -x flag is not enabledExamine the syslogd startup options found in the configuration. Look specifically for the presence of '-x' in the SYSLOGD_OPTIONS or startup flags. If -x is missing, reverse DNS lookups are performed by default.Affected if The -x flag is absent from syslogd startup options, meaning DNS lookups are enabled
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Confirm remote message reception is possibleCheck if syslogd is bound to 0.0.0.0:514 or :::514 (UDP) indicating it accepts remote messages. This can be done with 'netstat -anu | grep 514' or by reviewing syslogd config for -r flag.Affected if syslogd accepts remote messages (typically indicated by -r flag or binding to all interfaces)
You are affected if syslogd is running with remote reception enabled and the -x flag is NOT present in startup options, as reverse DNS lookups will be performed on spoofed source IPs.
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 dataEnable the -x flag in syslogd startup configuration to disable name lookups, preventing the daemon from performing reverse DNS lookups on incoming message sources.
Fix this in Linux Kernel
Scoped from the published advisory
- Consultation1.0 h
- Implementation1.0 h
- Testing1.0 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 $1,200.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2006-1624 — 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-2006-1624 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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