FreeBSD : ruby -- $SAFE escaping vulnerability about Exception#to_s/NameError#to_s (2a093853-2495-11e2-b0c7-000d601460a4)
Medium Nessus Plugin ID 62791
SynopsisThe remote FreeBSD host is missing one or more security-related updates.
DescriptionThe official ruby site reports :
Vulnerabilities found for Exception#to_s, NameError#to_s, and name_err_mesg_to_s() which is Ruby interpreter-internal API. A malicious user code can bypass $SAFE check by utilizing one of those security holes.
Ruby's $SAFE mechanism enables untrusted user codes to run in $SAFE >= 4 mode. This is a kind of sandboxing so some operations are restricted in that mode to protect other data outside the sandbox.
The problem found was around this mechanism. Exception#to_s, NameError#to_s, and name_err_mesg_to_s() interpreter-internal API was not correctly handling the $SAFE bits so a String object which is not tainted can destructively be marked as tainted using them. By using this an untrusted code in a sandbox can modify a formerly-untainted string destructively.
Ruby 1.8 once had a similar security issue. It fixed Exception#to_s and NameError#to_s, but name_err_mesg_to_str() issue survived previous security fix
SolutionUpdate the affected packages.