CVE-2026-125111

Description

Rack is a modular Ruby web server interface. Prior to 2.2.25, 3.1.23, and 3.2.8, Rack::Multipart::Parser can retain parsed data in its internal StringScanner buffer when reads end inside or immediately after multipart headers. An unauthenticated attacker can align many small parts with rack.multipart.buffer_size boundaries so the buffer grows with the request despite per-field, header, and preamble limits, causing a worker to exhaust memory. The attack requires only a well-formed multipart body and affects applications that parse multipart requests. This issue is fixed in versions 2.2.25, 3.1.23, and 3.2.8.

References

https://github.com/rubysec/ruby-advisory-db/blob/master/gems/rack/GHSA-5v64-555j-wjxm.yml

https://github.com/rack/rack/security/advisories/GHSA-5v64-555j-wjxm

https://github.com/rack/rack/commit/c9b4698595050838342bd3b5a0fc9ab908065f8f

https://github.com/rack/rack/commit/2eaa5b1026a03a43b6537b1a0b233707ba887702

https://github.com/rack/rack/commit/244e75a840cee0823f86d5d01dc374505a8abed8

https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-120485

Details

Source: Mitre, NVD

Risk Information

CVSS v2

CVSS v3

CVSS v4

EPSS