Rack's multipart parser buffers unbounded per-part headers, enabling DoS (memory exhaustion)
Summary
Rack's multipart parser buffers unbounded per-part headers, enabling DoS (memory exhaustion)
Original description
The description as published by the source.
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).
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2025-61772 ruby-rack Fixed in: 2.1.4-3+deb11u4
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- patch github.com
- patch github.com
- patch github.com