{"id":"UBUNTU-CVE-2026-34827","details":"Rack is a modular Ruby web server interface. From versions 3.0.0.beta1 to before 3.1.21, and 3.2.0 to before 3.2.6, Rack::Multipart::Parser#handle_mime_head parses quoted multipart parameters such as Content-Disposition: form-data; name=\"...\" using repeated String#index searches combined with String#slice! prefix deletion. For escape-heavy quoted values, this causes super-linear processing. An unauthenticated attacker can send a crafted multipart/form-data request containing many parts with long backslash-escaped parameter values to trigger excessive CPU usage during multipart parsing. This results in a denial of service condition in Rack applications that accept multipart form data. This issue has been patched in versions 3.1.21 and 3.2.6.","modified":"2026-06-30T18:15:52.931998125Z","published":"2026-04-02T18:16:00Z","related":["USN-8182-1"],"upstream":["CVE-2026-34827"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-34827"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-34827"},{"type":"REPORT","url":"https://github.com/rack/rack/security/advisories/GHSA-v6x5-cg8r-vv6x"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-8182-1"}],"affected":[{"package":{"name":"ruby-rack","ecosystem":"Ubuntu:Pro:14.04:LTS","purl":"pkg:deb/ubuntu/ruby-rack?arch=source&distro=esm-infra-legacy%2Ftrusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.5.2-1","1.5.2-1ubuntu0.1~esm1","1.5.2-3+deb8u3ubuntu1~esm2","1.5.2-3+deb8u3ubuntu1~esm3","1.5.2-3+deb8u3ubuntu1~esm4","1.5.2-3+deb8u3ubuntu1~esm6","1.5.2-3+deb8u3ubuntu1~esm7","1.5.2-3+deb8u3ubuntu1~esm8","1.5.2-3+deb8u3ubuntu1~esm9","1.5.2-3+deb8u3ubuntu1~esm10","1.5.2-3+deb8u3ubuntu1~esm11"],"ecosystem_specific":{"binaries":[{"binary_name":"librack-ruby","binary_version":"1.5.2-3+deb8u3ubuntu1~esm11"},{"binary_name":"librack-ruby1.8","binary_version":"1.5.2-3+deb8u3ubuntu1~esm11"},{"binary_name":"librack-ruby1.9.1","binary_version":"1.5.2-3+deb8u3ubuntu1~esm11"},{"binary_version":"1.5.2-3+deb8u3ubuntu1~esm11","binary_name":"ruby-rack"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34827.json"}},{"package":{"name":"ruby-rack","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/ruby-rack?arch=source&distro=esm-apps%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.5.2-4","1.6.4-2","1.6.4-3","1.6.4-3ubuntu0.1","1.6.4-3ubuntu0.2","1.6.4-3ubuntu0.2+esm1","1.6.4-3ubuntu0.2+esm2","1.6.4-3ubuntu0.2+esm4","1.6.4-3ubuntu0.2+esm5","1.6.4-3ubuntu0.2+esm6","1.6.4-3ubuntu0.2+esm7","1.6.4-3ubuntu0.2+esm8","1.6.4-3ubuntu0.2+esm9","1.6.4-3ubuntu0.2+esm10"],"ecosystem_specific":{"binaries":[{"binary_version":"1.6.4-3ubuntu0.2+esm10","binary_name":"ruby-rack"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34827.json"}},{"package":{"name":"ruby-rack","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/ruby-rack?arch=source&distro=esm-apps%2Fbionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.6.4-4","1.6.4-4ubuntu0.1","1.6.4-4ubuntu0.2","1.6.4-4ubuntu0.2+esm1","1.6.4-4ubuntu0.2+esm2","1.6.4-4ubuntu0.2+esm4","1.6.4-4ubuntu0.2+esm5","1.6.4-4ubuntu0.2+esm6","1.6.4-4ubuntu0.2+esm7","1.6.4-4ubuntu0.2+esm8","1.6.4-4ubuntu0.2+esm9","1.6.4-4ubuntu0.2+esm10"],"ecosystem_specific":{"binaries":[{"binary_name":"ruby-rack","binary_version":"1.6.4-4ubuntu0.2+esm10"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34827.json"}},{"package":{"name":"ruby-rack","ecosystem":"Ubuntu:Pro:20.04:LTS","purl":"pkg:deb/ubuntu/ruby-rack?arch=source&distro=esm-apps%2Ffocal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.6-3","2.0.7-2","2.0.7-2ubuntu0.1","2.0.7-2ubuntu0.1+esm1","2.0.7-2ubuntu0.1+esm2","2.0.7-2ubuntu0.1+esm3","2.0.7-2ubuntu0.1+esm4","2.0.7-2ubuntu0.1+esm5","2.0.7-2ubuntu0.1+esm6","2.0.7-2ubuntu0.1+esm7","2.0.7-2ubuntu0.1+esm8","2.0.7-2ubuntu0.1+esm9","2.0.7-2ubuntu0.1+esm10"],"ecosystem_specific":{"binaries":[{"binary_name":"ruby-rack","binary_version":"2.0.7-2ubuntu0.1+esm10"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34827.json"}},{"package":{"name":"ruby-rack","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/ruby-rack?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.1.4-3","2.1.4-4","2.1.4-5","2.1.4-5ubuntu1","2.1.4-5ubuntu1.1","2.1.4-5ubuntu1.2"],"ecosystem_specific":{"binaries":[{"binary_name":"ruby-rack","binary_version":"2.1.4-5ubuntu1.2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34827.json"}},{"package":{"name":"ruby-rack","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/ruby-rack?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.2.4-3","2.2.7-1","2.2.7-1ubuntu0.1","2.2.7-1ubuntu0.2","2.2.7-1ubuntu0.3","2.2.7-1ubuntu0.4","2.2.7-1ubuntu0.5","2.2.7-1ubuntu0.6","2.2.7-1ubuntu0.7"],"ecosystem_specific":{"binaries":[{"binary_name":"ruby-rack","binary_version":"2.2.7-1ubuntu0.7"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34827.json"}},{"package":{"name":"ruby-rack","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/ruby-rack?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.1.16-0.1ubuntu0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subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34827.json"}},{"package":{"name":"ruby-rack","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/ruby-rack?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.1.16-0.1","3.1.18-1","3.1.18-1build1","3.2.4-1ubuntu1"],"ecosystem_specific":{"binaries":[{"binary_name":"ruby-rack","binary_version":"3.2.4-1ubuntu1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34827.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"Ubuntu","score":"medium"}]}