CVE-2026-18477 — MEDIUM (4.4)

Vulnerability Description

A TOCTOU (Time-of-Check Time-of-Use) vulnerability in GNU tar's incremental dumpdir 'X' rename handling allows a local attacker with write access to a directory being backed up to influence the restore process if the attacker has access to the system where the restore is being performed. During restoration, files or directories may be created, renamed or overwritten outside the intended extraction directory. This could lead to unauthorized file modification or, in some cases, privilege escalation. Exploitation does not require the attacker to modify or craft the archive, and standard backup and restore workflows—including extracting into a newly created directory without using the -P option do not mitigate the issue.

CVSS Score

4.4

MEDIUM

CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:N

Attack Vector

LOCAL

Attack Complexity

HIGH

Privileges Required

LOW

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality

NONE

Integrity

HIGH

Availability

NONE

Related Weaknesses (CWE)

CWE-367

References

FAQ

What is CVE-2026-18477?

CVE-2026-18477 is a vulnerability with a CVSS score of 4.4 (MEDIUM). A TOCTOU (Time-of-Check Time-of-Use) vulnerability in GNU tar's incremental dumpdir 'X' rename handling allows a local attacker with write access to a directory being backed up to influence the restor...

How severe is CVE-2026-18477?

CVE-2026-18477 has been rated MEDIUM with a CVSS base score of 4.4/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-18477?

Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.