Vulnerability · Published Oct 7, 2025 · Assigned by GitHub_M
CVE-2025-61770Rack's unbounded multipart preamble buffering enables DoS (memory exhaustion)
High 7.5
In plain English
A high-severity uncontrolled resource consumption in rack from rack. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.9% (higher than 61% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:10 | cockpit-ha-cluster | 0.12.1-1.el10_1.1 | ALSA-2025:21036 |
| AlmaLinux:8 | pcs | 0.10.18-2.el8_10.7.alma.1 | ALSA-2025:19719 |
| AlmaLinux:9 | pcs | 0.11.10-1.el9_7.1 | ALSA-2025:20962 |
| AlmaLinux:8 | pcs-snmp | 0.10.18-2.el8_10.7.alma.1 | ALSA-2025:19719 |
| AlmaLinux:9 | pcs-snmp | 0.11.10-1.el9_7.1 | ALSA-2025:20962 |
| Debian:12 | ruby-rack | 2.2.20-0+deb12u1 | DEBIAN-CVE-2025-61770 |
| Debian:12 | ruby-rack | 2.2.20-0+deb12u1 | DSA-6048-1 |
| Debian:13 | ruby-rack | 3.1.18-1~deb13u1 | DSA-6048-1 |
| Debian:13 | ruby-rack | 3.1.18-1~deb13u1 | DEBIAN-CVE-2025-61770 |
| Debian:14 | ruby-rack | 3.1.18-1 | DEBIAN-CVE-2025-61770 |
| Rocky Linux:8 | pcs | 0:0.10.18-2.el8_10.7 | RLSA-2025:19719 |
| Rocky Linux:9 | pcs | 0:0.11.10-1.el9_7.1 | RLSA-2025:20962 |
| Rocky Linux:9 | pcs | 0:0.11.9-2.el9_6.2 | RLSA-2025:19512 |
| RubyGems | rack | 3.1.17 | GHSA-p543-xpfm-54cp |
| RubyGems | rack | 2.2.19 | GHSA-p543-xpfm-54cp |
| RubyGems | rack | 3.2.2 | GHSA-p543-xpfm-54cp |
| Ubuntu:22.04:LTS | ruby-rack | 2.1.4-5ubuntu1.2 | UBUNTU-CVE-2025-61770 |
| Ubuntu:24.04:LTS | ruby-rack | 2.2.7-1ubuntu0.5 | UBUNTU-CVE-2025-61770 |
| Ubuntu:25.10 | ruby-rack | 3.1.16-0.1ubuntu0.1 | UBUNTU-CVE-2025-61770 |
Affected products (as reported)
Weakness: CWE-400 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- https://github.com/rack/rack/security/advisories/GHSA-p543-xpfm-54cp x_refsource_CONFIRM
- https://github.com/rack/rack/commit/589127f4ac8b5cf11cf88fb0cd116ffed4d2181e x_refsource_MISC
- https://github.com/rack/rack/commit/d869fed663b113b95a74ad53e1b5cae6ab31f29e x_refsource_MISC
- https://github.com/rack/rack/commit/e08f78c656c9394d6737c022bde087e0f33336fd x_refsource_MISC