CVE-2026-18477

Summary

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.

Affected Software

VendorProductVersion RangeStatus

Weaknesses

  • CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition

Workarounds

Avoid restoring incremental backups on systems where untrusted users have shell access, particularly if they could have modified or controlled any of the backed-up data. When restoring backups containing user-controlled content, perform the restoration only on systems that are inaccessible to those users.

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References