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CVE-2018-6954

Published: 13 February 2018

systemd-tmpfiles in systemd through 237 mishandles symlinks present in non-terminal path components, which allows local users to obtain ownership of arbitrary files via vectors involving creation of a directory and a file under that directory, and later replacing that directory with a symlink. This occurs even if the fs.protected_symlinks sysctl is turned on.

Notes

AuthorNote
mdeslaur
original fix was incomplete, see second pull
chrisccoulson
Fix reverted in xenial because it breaks containers running
on pre-2.6.39 kernels
mdeslaur
fix was re-introduced in xenial in 229-4ubuntu21.15

Priority

Medium

Cvss 3 Severity Score

7.8

Score breakdown

Status

Package Release Status
systemd
Launchpad, Ubuntu, Debian
artful Ignored
(end of life)
bionic
Released (237-3ubuntu10.9)
cosmic
Released (239-7ubuntu10.4)
trusty Not vulnerable
(binary not built)
upstream Needs triage

xenial
Released (229-4ubuntu21.15)
Patches:
upstream: https://github.com/systemd/systemd/pull/8358
upstream: https://github.com/systemd/systemd/pull/8822
upstream: https://github.com/systemd/systemd/commit/936f6bdb803c432578e2cdcc5f93f3bfff93aff0

Severity score breakdown

Parameter Value
Base score 7.8
Attack vector Local
Attack complexity Low
Privileges required Low
User interaction None
Scope Unchanged
Confidentiality High
Integrity impact High
Availability impact High
Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H