Posted by usa on 12 Oct 2012
A vulnerability was found that file creation routines can create unintended files by strategically inserting NUL(s) in file paths. This vulnerability has been reported as CVE-2012-4522.
Details
Ruby can handle arbitrary binary patterns as Strings, including NUL chars. On the other hand OSes and other libraries tend not. They usually treat a NUL as an End of String mark. So to interface them with Ruby, NUL chars should properly be avoided.
However methods like IO#open did not check the filename passed to them, and just passed those strings to lower layer routines. This led to create unintentional files like this:
p File.exists?("foo") #=> false
open("foo\0bar", "w") { |f| f.puts "hai" }
p File.exists?("foo") #=> true
p File.exists?("foo\0bar") #=> raises ArgumentError
Affected versions
- All Ruby 1.9.3 prior to patchlevel 286
- All development branches of Ruby 2.0.0 prior to revision r37163
Solution
Upgrade to a latest version.
Credit
This issue was reported by Peter Bex.
Updates
- Fixed typo at 2012-10-19 14:54:49 JST.
- Added a mention about CVE number at 2012-10-16 08:58:51 JST.
- Originally published at 2012-10-12 19:19:55 JST.