CVE-2025-61770

Publication date 7 October 2025

Last updated 15 January 2026

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

7.5 · High

Score breakdown

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` 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.

Status

Package Ubuntu Release Status
ruby-rack 25.10 questing
Fixed 3.1.16-0.1ubuntu0.1
25.04 plucky Ignored end of life, was needed
24.04 LTS noble
Fixed 2.2.7-1ubuntu0.5
22.04 LTS jammy
Fixed 2.1.4-5ubuntu1.2
20.04 LTS focal Ignored changes too intrusive
18.04 LTS bionic Ignored changes too intrusive
16.04 LTS xenial Ignored changes too intrusive
14.04 LTS trusty Ignored changes too intrusive

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package Patch details
ruby-rack

Severity score breakdown

Parameter Value
Base score 7.5 · High
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Scope Unchanged
Confidentiality None
Integrity impact None
Availability impact High
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

Related Ubuntu Security Notices (USN)

Other references