# CVE-2026-75593: BuildKit: Malicious client can bypass destination directory validation on local sources upload

CVE-2026-75593 is fixed in runfinch-finch on 1 platform by ALAS2023-2026-3140 (version 1.19.0-1.amzn2023.0.1), released September 28, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-75593
- Priority: High
- CVSS: n/a (Important)
- EPSS: 0.0054
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 23, 2026
- Weakness: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-75593

## Description

BuildKit is a toolkit for converting source code to build artifacts in an efficient, expressive and repeatable manner. Prior to 0.31.2, a custom client can produce such an upload request to the BuildKit daemon that files can escape from the BuildKit-controlled state directory. The client needs to have valid permissions to access BuildKit control API to issue builds, eg., bypass authentication, etc. This issue is fixed in version 0.31.2.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | runfinch-finch amzn 2023 | 1.19.0-1.amzn2023.0.1 | [ALAS2023-2026-3140](https://patchblox.com/security/data/fix/linux/alas2023-2026-3140.md) | Sep 28, 2026 |

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Data as of 2026-11-11T13:47:35Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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