Description

Rack provides an interface for developing web applications in Ruby. Prior to versions 2.2.11, 3.0.12, and 3.1.10, Rack::CommonLogger can be exploited by crafting input that includes newline characters to manipulate log entries. The supplied proof-of-concept demonstrates injecting malicious content into logs. When a user provides the authorization credentials via Rack::Auth::Basic, if success, the username will be put in env['REMOTE_USER'] and later be used by Rack::CommonLogger for logging purposes. The issue occurs when a server intentionally or unintentionally allows a user creation with the username contain CRLF and white space characters, or the server just want to log every login attempts. If an attacker enters a username with CRLF character, the logger will log the malicious username with CRLF characters into the logfile. Attackers can break log formats or insert fraudulent entries, potentially obscuring real activity or injecting malicious data into log files. Versions 2.2.11, 3.0.12, and 3.1.10 contain a fix.

Weaknesses 2

Affected Products 3

References 3

• github.com https://github.com/rack/rack/commit/074ae244430cda05c27ca91cda699709cfb3ad8e
  Patch
• github.com https://github.com/rack/rack/security/advisories/GHSA-7g2v-jj9q-g3rg
  ExploitVendor Advisory
• lists.debian.org https://lists.debian.org/debian-lts-announce/2025/03/msg00016.html

Remediation

• github.com https://github.com/rack/rack/commit/074ae244430cda05c27ca91cda699709cfb3ad8e
  Patch