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High severityNVD Advisory· Published Oct 7, 2025· Updated Oct 7, 2025

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

CVE-2025-61772

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).

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Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
rackRubyGems
< 2.2.192.2.19
rackRubyGems
>= 3.1, < 3.1.173.1.17
rackRubyGems
>= 3.2, < 3.2.23.2.2

Affected products

145

Patches

Vulnerability mechanics

References

7

News mentions

0

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