PHP internally uses hashtables to store arrays. The above creates a hashtable with 100% collisions (i.e. all keys will have the same hash). [...] Because every hash function has collisions this C array doesn't actually store the value we want, but a linked list of possible values. [...] Normally there will be only a small number of collisions, so in most cases the linked list will only have one value. But the [included script] creates a hash where all elements collide.

He explains why it works, noting that it's relatively simple to do in PHP because of how it applies a table mask. The slowness comes in when PHP is forced to go through the entire list when it tries to insert. Because of this issue, there's the potential for a Denial of Service attack that could potentially take a server down. There's a fix already in place for the problem, though, so keep an eye out for the next release (that will include a max_input_vars setting to prevent it).

rPath has issued an update for gd and multiple php packages. This fixes some vulnerabilities, where some have an unknown impact and others can potentially be exploited to cause a DoS (Denial of Service).

The update is marked as "moderately critical" so it's recommended that users update their installations as soon as possible. You can find out more information and get the links to download the packages from the original advisory post.

Debian has issued an update for php4/5. This fixes some vulnerabilities, which can be exploited by malicious people to conduct cross-site scripting attacks, cause a DoS (Denial of Service), and potentially compromise a vulnerable system.

You can get more information and links to the downloads here:

• PHP4 announcement
• PHP5 announcement

Slackware has issued an update for php5. This fixes some vulnerabilities, where one has an unknown impact and others can be exploited by malicious people to bypass certain security restrictions and cause a DoS (Denial of Service).

You can grab the updated packages via the original advisory and bring your installation up to date with the latest security fixes.

The vulnerability is caused due to the incorrect use of libpng within the function "gdPngReadData()" in ext/gd/libgd/gd_png.c of the GD extension when processing truncated data. This can be exploited to cause an infinite loop by e.g. tricking an application to process a specially crafted file. (reported by Xavier Roche)

This issue has been confirmed in PHP versions 4.4.7 and 5.2.2 but may affect others. The issue has already been corrected, however, and can be fetched from the PHP CVS system to protect your system.

Ubuntu has issued an update for php. This fixes some vulnerabilities, which can be exploited by malicious users to disclose potentially sensitive information, bypass certain security restrictions, gain escalated privileges, cause a DoS (Denial of Service), compromise a vulnerable system, and by malicious people to disclose potentially sensitive information, bypass certain security restrictions, cause a DoS (Denial of Service), and potentially compromise a vulnerable system.

The Secunia post has links to all of the packages you'll need (for each kind of architecture) to get things up to date and corrected. This issue has been marked as "Moderately Critical".