CVE-2017-18078

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2018-01-29 · updated 2026-06-17
Weakness: CWE-59

Description

systemd-tmpfiles in systemd before 237 attempts to support ownership/permission changes on hardlinked files even if the fs.protected_hardlinks sysctl is turned off, which allows local users to bypass intended access restrictions via vectors involving a hard link to a file for which the user lacks write access, as demonstrated by changing the ownership of the /etc/passwd file.

Affected products

Debian Linux: 8.0
openSUSE Leap: 42.3
systemd: before 237 — fixed in 237

How to fix

Upgrade to a fixed version: systemd 237. Check the vendor advisory for mitigations.

References

http://lists.opensuse.org/opensuse-updates/2018-02/msg00109.html
http://packetstormsecurity.com/files/146184/systemd-Local-Privilege-Escalation.html
http://www.openwall.com/lists/oss-security/2018/01/29/3
https://github.com/systemd/systemd/issues/7736
https://lists.apache.org/thread.html/r58af02e294bd07f487e2c64ffc0a29b837db5600e33b6e698b9d696b%40%3Cissues.bookkeeper.apache.org%3E
https://lists.apache.org/thread.html/rf4c02775860db415b4955778a131c2795223f61cb8c6a450893651e4%40%3Cissues.bookkeeper.apache.org%3E
https://lists.debian.org/debian-lts-announce/2019/04/msg00022.html
https://www.exploit-db.com/exploits/43935/
https://www.openwall.com/lists/oss-security/2018/01/29/4
http://lists.opensuse.org/opensuse-updates/2018-02/msg00109.html
http://packetstormsecurity.com/files/146184/systemd-Local-Privilege-Escalation.html
http://www.openwall.com/lists/oss-security/2018/01/29/3

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