Drupal RCE Vulnerability Requires Immediate Patching

Drupal, the widely popular content management system for websites, has been found to have a "highly critical" remote code execution (RCE) vulnerability that requires immediate patching.

The vulnerability (CVE-2018-7600) could allow complete takeover of the affected site from "multiple attack vectors," according to the Drupal team. It has a risk score of 21/25.

The result of the problem is that any visitor, no matter what privileges that they have been assigned, can gain access to, modify and delete private data.

(Source: Flickr)

According to Drupal, the RCE affects the Bootstrap system. The file that needs patching is located in /apps/drupalhome/includes/bootstrap.inc. The developer team also notes that the vulnerability is activated through either maliciously formed cookies, POST requests or query strings. That would mean that the maintenance page or the user/login may also be vulnerable. So, simply turning the site maintenance mode active will not work since that module uses Bootstrap.

It seems that the vulnerability lies within the logic of Drupal's PHP code -- in that it does not allow for necessary input validation.

Drupal has written in a FAQ section that this RCE problem is not currently active in the wild. However, engineers do expect attackers to develop exploits very soon after the announcement, hence their advice to immediately upgrade or patch.

The problem affects versions 6,7, and 8. Version 7.58 and 8.51 are the latest Drupal versions, and are deemed by Drupal not to have the RCE problem. Since Drupal 6 is on end-of-life status, Drupal recommends contacting the long-term D6 vendors for support and patches.

Patches are also available if immediate upgrading cannot be accomplished, but Drupal does recommend that their use only be temporary until a full upgrade can be performed.

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If patching cannot be done immediately, Drupal points to other mitigation methods.

These methods are all based on the idea of not serving vulnerable Drupal pages to visitors. According to Drupal:

"Temporarily replacing your Drupal site with a static HTML (ed. -- static here means an invariant page with no database accessing performed) page is an effective mitigation. For staging or development sites you could disable the site or turn on a "Basic Auth" password to prevent access to the site."

Cloudflare has pushed out a Drupal Web Application Firewall Rule to address the exploit. This doesn't directly help Nginx or Apache users, however.

The Drupal response to the RCE is seemingly exactly what one would want to happen. The team acted responsibly by not hiding it or downplaying it, and have provided a wide range of ways to mediate the problem.

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— Larry Loeb has written for many of the last century's major "dead tree" computer magazines, having been, among other things, a consulting editor for BYTE magazine and senior editor for the launch of WebWeek.