CVE-2025-61770

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` buffers the entire multipart preamble (bytes before the first boundary) in memory without any size limit. A client can send a large preamble followed by a valid boundary, causing significant memory use and potential process termination due to out-of-memory (OOM) conditions. Remote attackers can trigger large transient memory spikes by including a long preamble in multipart/form-data requests. The impact scales with allowed request sizes and concurrency, potentially causing worker crashes or severe slowdown due to garbage collection. Versions 2.2.19, 3.1.17, and 3.2.2 enforce a preamble size limit (e.g., 16 KiB) or discard preamble data entirely. Workarounds include limiting total request body size at the proxy or web server level and monitoring memory and set per-process limits to prevent OOM conditions.

Affected products

Almalinux, Centos, Debian, Linuxmint, Rack, Red Hat, Red Os, Rocky Linux

Rack

< 2.2.19, 3.1.17, 3.2.2

Fix

Available

CVSS 3.1

7.5 HIGH

EPSS

0.9% (55th percentile)

Weakness

CWE-400

NVD status

Analyzed

Published

2025-10-07

No exploit for CVE-2025-61770 has been indexed yet. Our index is built from live traffic and upstream syncs, so this page can only say what it knows — not that no exploit exists.