Linux Distributions Affected by Two “mailx” Vulnerabilities

Several Linux distributions are affected by a couple of security holes found in “mailx,” a utility that’s used for sending and receiving mail.

The vulnerabilities, which have been rated “moderate,” are caused by the way mailx handles the parsing of email addresses. A local attacker can use a syntactically valid email address to cause mailx to execute arbitrary shell commands (CVE-2014-7844). An attacker can also execute commands by leveraging the fact that mailx interprets shell meta-characters in certain email addresses (CVE-2004-2771).

The security holes, found in both the BSD mailx and Heirloom mailx implementations, affect Red Hat Enterprise Linux, CentOS, Debian, Ubuntu, and possibly other distros. Patches have already been made available for many of the operating systems and users are advised to update their packages.

Debian has pointed out that CVE-2004-2771 is a historic vulnerability already fixed in Debian’s bsd-mailx package.

“Note that this security update does not remove all mailx facilities for command execution, though. Scripts which send mail to addresses obtained from an untrusted source (such as a web form) should use the — separator before the email addresses (which was fixed to work properly in this update), or they should be changed to invoke mail -t or sendmail -i -t instead, passing the recipient addresses as part of the mail header,” Debian noted in its security advisory.

Red Hat posted a similar note in its own advisory.

“Note: Applications using mailx to send email to addresses obtained from untrusted sources will still remain vulnerable to other attacks if they accept email addresses which start with ‘-‘ (so that they can be confused with mailx options). To counteract this issue, this update also introduces the ‘–‘ option, which will treat the remaining command line arguments as email addresses,” the advisory reads.

This isn’t the first time several Unix-like operating systems are affected by the same vulnerability. In October, a security hole that could have been leveraged to execute arbitrary commands (CVE-2014-8517) was identified in the tnftp FTP client.

Earlier this month, researchers reported uncovering a buffer overflow vulnerability in a FreeBSD library that could lead to data corruption or arbitrary code execution (CVE-2014-8611).