# CVE-2026-85396: rubyzip before 3.4.0 Path Traversal in Zip::Entry#extract via Sibling-Directory Prefix

CVE-2026-85396 is fixed in ruby-zip on 1 platform by DEBIAN-CVE-2026-85396 (version 3.4.0+dfsg-1), released September 4, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-85396
- Priority: High
- CVSS: 7.5 (Important)
- EPSS: 0.0056
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 3, 2026
- Weakness: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-85396

## Description

rubyzip versions before 3.4.0 contain a path traversal vulnerability in Zip::Entry#extract that fails to properly validate extraction paths using prefix comparison without trailing separators. Attackers can craft archive entries with names like ../upload_backup/owned.sh to write files outside the intended extraction directory into sibling paths sharing the destination prefix.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | ruby-zip Debian 14 | 3.4.0+dfsg-1 | [DEBIAN-CVE-2026-85396](https://patchblox.com/security/data/fix/linux/debian-cve-2026-85396.md) | Sep 4, 2026 |

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Data as of 2026-11-08T00:53:09Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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