{"id":"CVE-2026-34829","aliases":["GHSA-8vqr-qjwx-82mw"],"url":"https://o3.security/vulnerability/CVE-2026-34829","summary":"Rack: Denial of Service via Unbounded Multipart File Upload Without Content-Length","details":"Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Multipart::Parser only wraps the request body in a BoundedIO when CONTENT_LENGTH is present. When a multipart/form-data request is sent without a Content-Length header, such as with HTTP chunked transfer encoding, multipart parsing continues until end-of-stream with no total size limit. For file parts, the uploaded body is written directly to a temporary file on disk rather than being constrained by the buffered in-memory upload limit. An unauthenticated attacker can therefore stream an arbitrarily large multipart file upload and consume unbounded disk space. This results in a denial of service condition for Rack applications that accept multipart form data. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.","published":"2026-04-02T16:46:47.357Z","modified":"2026-07-27T03:56:25.815974356Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"RubyGems","name":"rack","fixedVersion":"2.2.23"},{"ecosystem":"RubyGems","name":"rack","fixedVersion":"3.1.21"},{"ecosystem":"RubyGems","name":"rack","fixedVersion":"3.2.6"}],"fix":null,"references":[{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34829.json"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-34829"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34829.json"},{"type":"ADVISORY","url":"https://github.com/rack/rack/security/advisories/GHSA-8vqr-qjwx-82mw"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-34829"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2454488"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-27T03:56:25.815974356Z"}}