WEBrick 1.3.1 in Ruby 1.8.6 through patchlevel 383, 1.8.7 through patchlevel 248, 1.8.8dev, 1.9.1 through patchlevel 376, and 1.9.2dev writes data to a log file without sanitizing non-printable characters, which might allow remote attackers to modify a window's title, or possibly execute arbitrary commands or overwrite files, via an HTTP request containing an escape sequence for a terminal emulator.

Directory traversal vulnerability in WEBrick in Ruby 1.8 before 1.8.5-p115 and 1.8.6-p114, and 1.9 through 1.9.0-1, when running on systems that support backslash (\) path separators or case-insensitive file names, allows remote attackers to access arbitrary files via (1) "..%5c" (encoded backslash) sequences or (2) filenames that match patterns in the :NondisclosureName option.

DISPUTED The WEBrick gem 1.4.2 for Ruby allows directory traversal if the attacker once had local access to create a symlink to a location outside of the web root directory. NOTE: The vendor states that this is analogous to Options FollowSymlinks in the Apache HTTP Server, and therefore it is "not a problem."

http://www.ruby-lang.org/en/news/2008/03/03/webrick-file-access-vulnerability/

WEBrick, a standard library of Ruby to implement HTTP servers, has file access vulnerability.

1. Systems that accept backslash (\) as a path separator, such as Windows. 2. Systems that use case insensitive filesystems such as NTFS on Windows, HFS on Mac OS X.

Attacker can access private files by sending a url with url encoded backslash (\). This works only on systems that accept backslash as a path separator. Or they could bypass restrictions with case-insensitive filesystems.