Medium [CVE-2026-16552] systemd-tmpfiles symlink-redirected arbitrary file overwrite via a CHASE_SAFE root-to-unprivileged ownership transition bypass
This medium-severity Red Hat Linux advisory covers CVE-2026-16552.
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Summary
[REJECTED] A flaw was found in systemd-tmpfiles. When processing a tmpfiles.d configuration entry that writes to a file, systemd-tmpfiles can follow a symbolic link placed by an unprivileged local user, and an existing safety check does not detect this specific case because it always treats transitions away from the root user as safe.
On systems where a tmpfiles.d configuration targets a path an unprivileged user can influence, this could allow that user to redirect a privileged systemd-tmpfiles write to a file of their choosing, though the content written remains determined by the existing configuration rather than by the unprivileged user.
The highest threat from this vulnerability is to integrity. This CVE has been marked as rejected by the assigning CNA.
Red Hat severity: not rated — CVSS 0 (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:N). Weakness: CWE-59.
Red Hat lists Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Red Hat Hardened Images; Red Hat OpenShift Container Platform 4 as not affected.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 9 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 9 days ago·verify at source
Mitigation checklist
- Restrict or audit any custom tmpfiles.d configuration entries (e.g. authored via configuration-management tooling) that use the 'w' item type against paths under /run/user/*, per-user home directories, or other locations where an unprivileged user can influence path resolution, until an upstream fix is available.
Official advisory · high-confidence parse· fetched 9 days ago·verify at source
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