Vulnerability details

Rack is a modular Ruby web server interface. In versions prior to 2.2.19, 3.1.17, and 3.2.2, `Rack::Multipart::Parser` can accumulate unbounded data when a multipart part’s header block never terminates with the required blank line (`CRLFCRLF`). The parser keeps appending incoming bytes to memory without a size cap, allowing a remote attacker to exhaust memory and cause a denial of service (DoS). Attackers can send incomplete multipart headers to trigger high memory use, leading to process termination (OOM) or severe slowdown. The effect scales with request size limits and concurrency. All applications handling multipart uploads may be affected. Versions 2.2.19, 3.1.17, and 3.2.2 cap per-part header size (e.g., 64 KiB). As a workaround, restrict maximum request sizes at the proxy or web server layer (e.g., Nginx `client_max_body_size`).

• https://github.com/rack/rack/security/advisories/GHSA-wpv5-97wm-hp9c x_refsource_CONFIRM
• https://github.com/rack/rack/commit/589127f4ac8b5cf11cf88fb0cd116ffed4d2181e x_refsource_MISC
• https://github.com/rack/rack/commit/d869fed663b113b95a74ad53e1b5cae6ab31f29e x_refsource_MISC
• https://github.com/rack/rack/commit/e08f78c656c9394d6737c022bde087e0f33336fd x_refsource_MISC