# CVE-2026-43617: Rsync < 3.4.3 Authorization Bypass via Hostname Resolution

CVE-2026-43617 is fixed in 4 products on 1 platform, first by rsync 3.1.2-2.1ubuntu1.6+esm3, released May 19, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-43617
- Priority: Routine
- CVSS: 4.8 (Moderate)
- EPSS: 0.0028
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 19, 2026
- Weakness: Authentication Bypass by Alternate Name
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-43617

## Description

Rsync version 3.4.2 and prior contain an authorization bypass vulnerability in the rsync daemon's hostname-based access control list enforcement when configured with chroot. Attackers can bypass hostname-based deny rules by controlling the PTR record for their source IP address, allowing connections from hostnames that administrators intended to deny when reverse DNS resolution fails and defaults to UNKNOWN.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | rsync Debian 12.15 (bookworm) | 3.2.7-1+deb12u5 | [DEBIAN-CVE-2026-43617](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43617.md) | May 27, 2026 |
| Linux | rsync Debian 13.5 (trixie) | 3.4.1+ds1-5+deb13u3 | [DEBIAN-CVE-2026-43617](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43617.md) | May 27, 2026 |
| Linux | rsync Debian 14 | 3.4.3+ds1-1 | [DEBIAN-CVE-2026-43617](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43617.md) | May 27, 2026 |
| Linux | rsync Ubuntu 18.04.6 LTS (bionic) | 3.1.2-2.1ubuntu1.6+esm3 | [rsync 3.1.2-2.1ubuntu1.6+esm3](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-rsync-3.1.2-2.1ubuntu1.6-esm3.md) | May 19, 2026 |
| Linux | rsync Ubuntu 20.04 LTS (focal) | 3.1.3-8ubuntu0.9+esm1 | [rsync 3.1.3-8ubuntu0.9+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-rsync-3.1.3-8ubuntu0.9-esm1.md) | May 19, 2026 |
| Linux | rsync Ubuntu 22.04.1 LTS (jammy) | 3.2.7-0ubuntu0.22.04.6 | [rsync 3.2.7-0ubuntu0.22.04.6](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-rsync-3.2.7-0ubuntu0.22.04.6.md) | May 27, 2026 |
| Linux | rsync Ubuntu 24.04.5 LTS (noble) | 3.2.7-1ubuntu1.4 | [rsync 3.2.7-1ubuntu1.4](https://patchblox.com/security/data/fix/linux/ubuntu-noble-rsync-3.2.7-1ubuntu1.4.md) | May 27, 2026 |
| Linux | rsync Ubuntu 25.10 (questing) | 3.4.1+ds1-5ubuntu1.2 | [rsync 3.4.1+ds1-5ubuntu1.2](https://patchblox.com/security/data/fix/linux/ubuntu-questing-rsync-3.4.1-ds1-5ubuntu1.2.md) | May 27, 2026 |
| Linux | rsync Ubuntu 26.04.1 LTS (resolute) | 3.4.1+ds1-7ubuntu0.2 | [rsync 3.4.1+ds1-7ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-rsync-3.4.1-ds1-7ubuntu0.2.md) | May 19, 2026 |
| Linux | rsync amzn 2023 | 3.5.1-1.amzn2023.0.1 | [ALAS2023-2026-3131](https://patchblox.com/security/data/fix/linux/alas2023-2026-3131.md) | Sep 28, 2026 |
| Linux | rsync opensuse-leap 16.0 | 3.4.1-160000.6.1 | [OPENSUSE-SU-2026:21650-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21650-1.md) | Aug 26, 2026 |
| Linux | rsync sles 16.0 | 3.4.1-160000.6.1 | [SUSE-SU-2026:23323-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23323-1.md) | Aug 26, 2026 |
| Linux | rsync-daemon amzn 2023 | 3.5.1-1.amzn2023.0.1 | [ALAS2023-2026-3131](https://patchblox.com/security/data/fix/linux/alas2023-2026-3131.md) | Sep 28, 2026 |
| Linux | rsync-debuginfo amzn 2023 | 3.5.1-1.amzn2023.0.1 | [ALAS2023-2026-3131](https://patchblox.com/security/data/fix/linux/alas2023-2026-3131.md) | Sep 28, 2026 |
| Linux | rsync-debugsource amzn 2023 | 3.5.1-1.amzn2023.0.1 | [ALAS2023-2026-3131](https://patchblox.com/security/data/fix/linux/alas2023-2026-3131.md) | Sep 28, 2026 |

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Data as of 2026-11-08T19:12:23Z 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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