CVE-2025-61772

Rack's multipart parser buffers unbounded per-part headers, enabling DoS (memory exhaustion)

Published Oct 7, 2025 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
Description
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`).

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4357-1 ruby-rack security update
Debian DSA Debian DSA DSA-6048-1 ruby-rack security update
Github GHSA Github GHSA GHSA-wpv5-97wm-hp9c Rack's multipart parser buffers unbounded per-part headers, enabling DoS (memory exhaustion)
History
Type Values Removed Values Added
CPEs cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*
Type Values Removed Values Added
First Time appeared Rack
Rack rack
Vendors & Products Rack
Rack rack
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description 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`).
Title Rack's multipart parser buffers unbounded per-part headers, enabling DoS (memory exhaustion)
Weaknesses CWE-400
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Oct 7, 2025, 5:51 PM
Reserved
Sep 30, 2025, 7:43 PM
Status
Analyzed
Published
Oct 7, 2025, 3:16 PM
Modified
Oct 19, 2026, 4:10 PM
Severity
Moderate
Public date
Oct 7, 2025, 3:02 PM