CVE-2026-18477: Tar: tar: toctou in incremental dumpdir 'x' rename handling allows restore path escape

mediumCVSS 4.4CVE-2026-18477

CSIRTS triage

vendor: GNU product: tar Path traversal

What: Time-of-check-time-of-use (TOCTOU) race condition in incremental dumpdir 'x' rename handling allows restore path escape.
Who is affected: Deployments using GNU tar for incremental backups with the 'x' option on multi-user systems.
Urgency: Medium urgency; requires race condition exploitation but enables directory traversal during restore.
Action: Update GNU tar to a patched version that properly locks file operations during incremental restore.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: medium — CVSS 4.4
Published: 2026-08-11
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-18477

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-184770.10% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 1% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-18477	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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