CVE-2026-18477
MediumCVSS 4.4Exploitation Probability (EPSS)
Low risk1th percentile - higher than 1% of all known CVEs
Summary
GNU tar has a TOCTOU vulnerability in incremental dumpdir 'X' rename handling. A local attacker with write access to a directory being backed up can influence the restore process if they have access to the system where the restore is performed. During restoration, files or directories may be created, renamed, or overwritten outside the intended extraction directory, potentially leading to unauthorized file modification or privilege escalation.
Risk Assessment
An attacker could exploit this vulnerability to overwrite system or configuration files outside the target directory, potentially leading to privilege escalation or system integrity compromise.
Recommendation
Update GNU tar to a version where the vulnerability is fixed, and avoid restoring archives from untrusted sources without proper safeguards.
Other vulnerabilities in GNU tar
See all- CVE-2016-6321High
Directory traversal vulnerability in the safer_name_suffix function in GNU tar versions 1.14 through 1.29 may allow remote attackers to bypass an intended protection mechanism and write to arbitrary files due to improper sanitization of the file_name parameter.
- CVE-2026-18508Medium
GNU tar has a vulnerability when extracting an archive with the --one-top-level option. Hardlink targets are not confined to the designated top-level directory and may resolve relative to the extraction working directory. A crafted archive can create hardlinks that escape the intended boundary and, when combined with a preexisting symbolic link under the working directory, may allow writing outside that boundary during a single extraction.
- CVE-1999-0202High
The GNU tar command, when used in FTP sessions, may allow an attacker to execute arbitrary commands.
Original NVD description (English source)
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.