ruby-rack: Rack is a modular Ruby web server interface
CVE-2026-26961 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.
Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Multipart::Parser extracts the boundary parameter from multipart/form-data using a greedy regular expression. When a Content-Type header contains multiple boundary parameters, Rack selects the last one rather than the first. In deployments where an upstream proxy, WAF, or intermediary interprets the first boundary parameter, this mismatch can allow an attacker to smuggle multipart content past upstream inspection and have Rack parse a different body structure than the intermediary validated. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| rmt-server · opensuse-leap 16.0 | 3.1.0-160000.1.1 | OPENSUSE-SU-2026:21640-1 | Aug 25, 2026 |
| rmt-server · sles 15.6 | 2.27-150500.3.47.1 | SUSE-SU-2026:2487-1 | Jun 22, 2026 |
| rmt-server · sles 16.0 | 3.1.0-160000.1.1 | SUSE-SU-2026:23321-1 | Aug 25, 2026 |
| ruby-rack · Debian 12.15 (bookworm) | 2.2.22-0+deb12u2 | DEBIAN-CVE-2026-26961 | Apr 2, 2026 |
| ruby-rack · Debian 13.5 (trixie) | 3.1.20-0+deb13u2 | DEBIAN-CVE-2026-26961 | Apr 2, 2026 |
| ruby-rack · Debian 14 | 3.2.6-2 | DEBIAN-CVE-2026-26961 | Apr 2, 2026 |
| ruby-rack · Ubuntu 22.04.1 LTS (jammy) | 2.1.4-5ubuntu1.2+esm3 | ruby-rack 2.1.4-5ubuntu1.2+esm3 | Apr 30, 2026 |
| ruby-rack · Ubuntu 24.04.5 LTS (noble) | 2.2.7-1ubuntu0.7 | ruby-rack 2.2.7-1ubuntu0.7 | Apr 30, 2026 |
| ruby-rack · Ubuntu 25.10 (questing) | 3.1.16-0.1ubuntu0.3 | ruby-rack 3.1.16-0.1ubuntu0.3 | Apr 30, 2026 |
| ruby-rack · Ubuntu 26.04.1 LTS (resolute) | 3.2.4-1ubuntu1.1 | ruby-rack 3.2.4-1ubuntu1.1 | Apr 2, 2026 |
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