Affected: rack

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: RubyGems: uri

There is a possibility for userinfo leakage by in the uri gem. This vulnerability has been assigned the CVE identifier CVE-2025-27221. We recommend upgrading the uri gem.

## Details

The methods `URI#join`, `URI#merge`, and `URI#+` retained userinfo, such as `user:password`, even after the host is replaced. When generating a URL to a malicious host from a URL containing secret userinfo using these methods, and having someone access that URL, an unintended userinfo leak could occur.

Please update URI gem to version 0.11.3, 0.12.4, 0.13.2, 1.0.3 or later.

## Affected versions

uri gem versions < 0.11.3, 0.12.0 to 0.12.3, 0.13.0, 0.13.1 and 1.0.0 to 1.0.2.

## Credits

Thanks to Tsubasa Irisawa (lambdasawa) for discovering this issue. Also thanks to nobu for additional fixes of this vulnerability.