CVE-2026-18508
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Hardlink Path Traversal in GNU tar

Publication date: 2026-08-03

Last updated on: 2026-08-03

Assigner: Red Hat, Inc.

Description
A flaw was found in GNU tar. 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.

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Meta Information

Published
2026-08-03
Last Modified
2026-08-03
Generated
2026-08-03
AI Q&A
2026-08-03
EPSS Evaluated
N/A
NVD
CVE-2026-18508
EUVD
EUVD-2026-52327

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
gnu tar *

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-59 The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

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Executive Summary

This vulnerability in GNU tar occurs when using the --one-top-level option. Hardlink targets in a crafted archive can escape the intended top-level directory and resolve relative to the extraction working directory. If combined with a preexisting symbolic link, it may allow writing outside the intended boundary during extraction.

Detection Guidance

This vulnerability can be detected by examining GNU tar behavior when using the --one-top-level option. Check if hardlink targets escape the intended directory during extraction. Review extraction logs for unexpected file writes outside the target directory.

Impact Analysis

An attacker could create a malicious tar archive that, when extracted, writes files outside the intended directory. This could lead to unauthorized file modifications or overwrites on your system, potentially causing data corruption or enabling further attacks.

Compliance Impact

This vulnerability could violate compliance requirements by allowing unauthorized file access or modification. For GDPR, it may risk data integrity or unauthorized exposure. For HIPAA, it could compromise protected health information integrity.

Mitigation Strategies

Avoid using the --one-top-level option with GNU tar until a patch is available. Use alternative extraction methods that do not rely on this option. Monitor for suspicious archive extractions and restrict write permissions in extraction directories.

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