CVE-2025-25184

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.

A flaw was found in the rubygem-rack package. When a user provides the authorization credentials via Rack::Auth::Basic, if successful, the username is placed in env['REMOTE_USER'] and later used by Rack::CommonLogger for logging purposes. The issue occurs when a server intentionally or unintentionally allows a user creation with the username containing CRLF and white space characters or the server logs every login attempt. If an attacker enters a username with a CRLF character, the logger will log the malicious username with CRLF characters into the logfile. This flaw allows attackers to break log formats or insert fraudulent entries, potentially obscuring activity or injecting malicious data into log files.

Nhật Thái Đỗ discovered that Rack incorrectly handled certain usernames. A remote attacker could possibly use this issue to perform CRLF injection. Phạm Quang Minh discovered that Rack incorrectly handled certain headers. A remote attacker could possibly use this issue to perform log injection. Phạm Quang Minh discovered that Rack did not properly handle relative file paths. A remote attacker could potentially exploit this to include local files that should have been inaccessible.