# CVE-2026-34786: ruby-rack: Rack is a modular Ruby web server interface

CVE-2026-34786 is fixed in 2 products on 1 platform, first by ruby-rack 3.2.4-1ubuntu1.1, released April 2, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-34786
- Priority: Routine
- CVSS: 5.3 (medium)
- EPSS: 0.0020
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 2, 2026

## Description

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Static#applicable_rules evaluates several header_rules types against the raw URL-encoded PATH_INFO, while the underlying file-serving path is decoded before the file is served. As a result, a request for a URL-encoded variant of a static path can serve the same file without the headers that header_rules were intended to apply. In deployments that rely on Rack::Static to attach security-relevant response headers to static content, this can allow an attacker to bypass those headers by requesting an encoded form of the path. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | rmt-server opensuse-leap 16.0 | 3.1.0-160000.1.1 | [OPENSUSE-SU-2026:21640-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21640-1.md) | Aug 25, 2026 |
| Linux | rmt-server sles 15.6 | 2.27-150500.3.47.1 | [SUSE-SU-2026:2487-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-2487-1.md) | Jun 22, 2026 |
| Linux | rmt-server sles 16.0 | 3.1.0-160000.1.1 | [SUSE-SU-2026:23321-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23321-1.md) | Aug 25, 2026 |
| Linux | ruby-rack Debian 12.15 (bookworm) | 2.2.22-0+deb12u2 | [DEBIAN-CVE-2026-34786](https://patchblox.com/security/data/fix/linux/debian-cve-2026-34786.md) | Apr 2, 2026 |
| Linux | ruby-rack Debian 13.5 (trixie) | 3.1.20-0+deb13u2 | [DEBIAN-CVE-2026-34786](https://patchblox.com/security/data/fix/linux/debian-cve-2026-34786.md) | Apr 2, 2026 |
| Linux | ruby-rack Debian 14 | 3.2.6-2 | [DEBIAN-CVE-2026-34786](https://patchblox.com/security/data/fix/linux/debian-cve-2026-34786.md) | Apr 2, 2026 |
| Linux | ruby-rack Ubuntu 18.04.6 LTS (bionic) | 1.6.4-4ubuntu0.2+esm10 | [ruby-rack 1.6.4-4ubuntu0.2+esm10](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-ruby-rack-1.6.4-4ubuntu0.2-esm10.md) | Apr 30, 2026 |
| Linux | ruby-rack Ubuntu 22.04.1 LTS (jammy) | 2.1.4-5ubuntu1.2+esm3 | [ruby-rack 2.1.4-5ubuntu1.2+esm3](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-ruby-rack-2.1.4-5ubuntu1.2-esm3.md) | Apr 30, 2026 |
| Linux | ruby-rack Ubuntu 24.04.5 LTS (noble) | 2.2.7-1ubuntu0.7 | [ruby-rack 2.2.7-1ubuntu0.7](https://patchblox.com/security/data/fix/linux/ubuntu-noble-ruby-rack-2.2.7-1ubuntu0.7.md) | Apr 30, 2026 |
| Linux | ruby-rack Ubuntu 25.10 (questing) | 3.1.16-0.1ubuntu0.3 | [ruby-rack 3.1.16-0.1ubuntu0.3](https://patchblox.com/security/data/fix/linux/ubuntu-questing-ruby-rack-3.1.16-0.1ubuntu0.3.md) | Apr 30, 2026 |
| Linux | ruby-rack Ubuntu 26.04.1 LTS (resolute) | 3.2.4-1ubuntu1.1 | [ruby-rack 3.2.4-1ubuntu1.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-ruby-rack-3.2.4-1ubuntu1.1.md) | Apr 2, 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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