CVE-2012-0871
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 session_link_x11_socket function in login/logind-session.c in systemd-logind in systemd, possibly 37 and earlier, allows local users to create or overwrite arbitrary files via a symlink attack on the X11 user directory in /run/user/.
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 confidenceThe session_link_x11_socket function in systemd-logind (versions 37 and earlier) fails to validate or sanitize the X11 socket directory path in /run/user/ before creation. This allows a local attacker to place a malicious symlink in the target directory location, causing systemd-logind to follow the symlink and create/overwrite files at an arbitrary filesystem location when the service creates its socket directory.
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<= 037= 1= 2= 3= 4= 5= 6= 7= 8= 9= 10= 11= 12.1CVSS 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
- None
- Integrity
- Complete
- Availability
- Complete
AV:L/AC:M/Au:N/C:N/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 systemd versionRun 'systemctl --version' or check the systemd package version with your package manager (e.g., 'rpm -q systemd' or 'dpkg -l systemd')Affected if The version is 37 or earlier, or falls within versions 1-11 as listed in affected versions
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Confirm systemd-logind is activeRun 'systemctl status systemd-logind' or check if the process is running with 'ps aux | grep systemd-logind'Affected if systemd-logind is running and the systemd version is vulnerable (see step 1)
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Check /run/user/ permissionsRun 'ls -la /run/user/' to inspect directory permissions and look for any unexpected symlinksAffected if The /run/user/ directory has weak permissions (world-writable or group-writable) or contains unexpected symlinks pointing outside /run/user/
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Verify X11 socket directory creation behaviorCheck if /run/user/<uid>/ is created when users log in via X11 (e.g., 'ls -la /run/user/0/' after an X11 login). Look for the x11 socket subdirectory.Affected if X11 session tracking is enabled and systemd-logind creates socket directories in /run/user/ with the vulnerable version
You are affected if running systemd version 37 or earlier (or versions 1-11) with systemd-logind active and X11 session tracking enabled, and /run/user/ has weak permissions allowing symlink injection.
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 systemd to a version beyond 37 which contains the patched session_link_x11_socket function. As a temporary workaround, ensure strict permissions on /run/user/ directories and monitor for unauthorized symlink creation.
- Consultation1.0 h
- Implementation2.0 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-2012-0871 — 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-2012-0871 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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