CVE-2017-13649
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 · uneditedUnrealIRCd 4.0.13 and earlier creates a PID file after dropping privileges to a non-root account, which might allow local users to kill arbitrary processes by leveraging access to this non-root account for PID file modification before a root script executes a "kill `cat /pathname`" command. NOTE: the vendor indicates that there is no common or recommended scenario in which a root script would execute this kill 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 · moderate confidenceUnrealIRCd 4.0.13 and earlier creates a PID file after dropping privileges to a non-root account. A local user with access to this non-root account could modify the PID file to point to an arbitrary process ID before a root script executes a 'kill `cat /pathname`' command, potentially causing arbitrary process termination. This is a TOCTOU (time-of-check-time-of-use) race condition combined with improper privilege separation.
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<= 4.0.13CVSS 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
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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 UnrealIRCd versionRun 'unrealircd -version' or check the binary with 'unrealircd -v' to determine the installed versionAffected if Version is 4.0.13 or earlier (e.g., 4.0.12, 4.0.11, etc.)
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Locate the PID fileCheck unrealircd.conf for the 'pidfile' directive, or common locations like /var/run/unrealircd.pid or /run/unrealircd.pidAffected if A PID file is configured and exists on the system
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Check for scripts using kill with PID fileSearch for shell scripts (in /etc/init.d/, /usr/local/etc/, etc.) that contain patterns like 'kill `cat /pathname/to/pidfile`' or 'kill $(cat /pathname/to/pidfile)'Affected if Any root-owned script executes kill on the PID file contents without additional safeguards
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Verify PID file ownership and permissionsRun 'ls -la' on the PID file path to check if it is owned by the unrealircd unprivileged user rather than root, and examine if it was created post-privilege-dropAffected if The PID file is owned by the non-root UnrealIRCd user account (privileges already dropped when created)
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Review startup scripts for TOCTOU windowExamine the startup sequence in init scripts or systemd units to determine if there is a time gap between when the UnrealIRCd process drops privileges and when the PID file is writtenAffected if The PID file is written after UnrealIRCd switches to a non-root user, creating a window where that user could modify the file before root scripts read it
A user is affected if running UnrealIRCd version 4.0.13 or earlier with a PID file created after privilege dropping and any root-level script uses 'kill' on that PID file contents.
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 dataThe PID file should be created before dropping privileges; alternatively, use secure file permissions or avoid root scripts that execute 'kill `cat /pathname`' patterns.
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-13649 — 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-2017-13649 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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