# CVE-2026-18508: Tar: tar: --one-top-level hardlink targets not confined to top-level directory enabling arbitrary file overwrite

CVE-2026-18508 is fixed in tar on 1 platform, first by RHSA-2026:61586, released July 31, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-18508
- Priority: Routine
- CVSS: 5.6 (Moderate)
- EPSS: 0.0014
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 31, 2026
- Weakness: Improper Link Resolution Before File Access ('Link Following')
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-18508

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | tar RHEL 10 | 1.35-13.el10_2 | [RHSA-2026:61586](https://patchblox.com/security/data/fix/linux/rhsa-2026-61586.md) | Jul 31, 2026 |
| Linux | tar RHEL 8 | 2:1.30-13.el8_10 | [RHSA-2026:70390](https://patchblox.com/security/data/fix/linux/rhsa-2026-70390.md) | Sep 23, 2026 |
| Linux | tar RHEL 9 | 2:1.34-13.el9_8 | [RHSA-2026:61581](https://patchblox.com/security/data/fix/linux/rhsa-2026-61581.md) | Sep 13, 2026 |
| Linux | tar almalinux 10 | 2:1.35-13.el10_2 | [ALSA-2026:61586](https://patchblox.com/security/data/fix/linux/alsa-2026-61586.md) | Aug 31, 2026 |
| Linux | tar almalinux 8 | 2:1.30-13.el8_10 | [ALSA-2026:70390](https://patchblox.com/security/data/fix/linux/alsa-2026-70390.md) | Sep 22, 2026 |
| Linux | tar almalinux 9 | 2:1.34-13.el9_8 | [ALSA-2026:61581](https://patchblox.com/security/data/fix/linux/alsa-2026-61581.md) | Aug 31, 2026 |
| Linux | tar ol 10 | 2:1.35-13.el10_2 | [ELSA-2026-61586-0](https://patchblox.com/security/data/fix/linux/elsa-2026-61586-0.md) | Sep 1, 2026 |
| Linux | tar ol 8 | 2:1.30-13.el8_10 | [ELSA-2026-70390](https://patchblox.com/security/data/fix/linux/elsa-2026-70390.md) | Sep 23, 2026 |
| Linux | tar ol 9 | 2:1.34-13.el9_8 | [ELSA-2026-61581-0](https://patchblox.com/security/data/fix/linux/elsa-2026-61581-0.md) | Sep 1, 2026 |
| Linux | tar rocky 10 | 2:1.35-13.el10_2 | [RLSA-2026:61586](https://patchblox.com/security/data/fix/linux/rlsa-2026-61586.md) | Sep 11, 2026 |
| Linux | tar rocky 8 | 2:1.30-13.el8_10 | [RLSA-2026:70390](https://patchblox.com/security/data/fix/linux/rlsa-2026-70390.md) | Sep 24, 2026 |
| Linux | tar rocky 9 | 2:1.34-13.el9_8 | [RLSA-2026:61581](https://patchblox.com/security/data/fix/linux/rlsa-2026-61581.md) | Sep 1, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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