The PHP development team would like to announce the immediate availability of PHP 5.4.2. This release delivers a security fix.
There is a vulnerability in certain CGI-based setups that has gone unnoticed for at least 8 years. Section 7 of the CGI spec states:
Some systems support a method for supplying a array of strings to the CGI script. This is only used in the case of an `indexed' query. This is identified by a "GET" or "HEAD" HTTP request with a URL search string not containing any unencoded "=" characters.So requests that do not have a "=" in the query string are treated differently from those who do in some CGI implementations. For PHP this means that a request containing ?-s may dump the PHP source code for the page, but a request that has ?-s&a=1 is fine.
A large number of sites run PHP as either an Apache module through mod_php or using php-fpm under nginx. Neither of these setups are vulnerable to this. Straight shebang-style CGI also does not appear to be vulnerable.
If you are using Apache mod_cgi to run PHP you may be vulnerable. To see if you are just add ?-s to the end of any of your URLs. If you see your source code, you are vulnerable. If your site renders normally, you are not.
Making a bad week worse, we had a bug in our bug system that toggled the private flag of a bug report to public on a comment to the bug report causing this issue to go public before we had time to test solutions to the level we would like.
To fix this update to PHP 5.3.12 or PHP 5.4.2. We recognize that since this is a rather outdated way to run PHP it may not be feasible to upgrade these sites to a modern version of PHP, so an alternative is to configure your web server to not let these types of requests with query strings starting with a "-" and not containing a "=" through. Adding a rule like this should not break any sites. For Apache using mod_rewrite it would look like this:
RewriteCond %{QUERY_STRING} ^(%2d|-)[^=]+$ [NC]
RewriteRule ^(.*) $1? [L]
If you are writing your own rule, be sure to take the urlencoded ?%2ds version into account.
For source downloads of PHP 5.4.2 please visit our downloads page, Windows binaries can be found on windows.php.net/download/. A ChangeLog exists.