Why mail() is dangerous in PHP

3 May 2017 by Robin Peraglie
Email Security in PHP

During our advent of PHP application vulnerabilities, we reported a remote command execution vulnerability in the popular webmailer Roundcube (CVE-2016-9920). This vulnerability allowed a malicious user to execute arbitrary system commands on the targeted server by simply writing an email via the Roundcube interface. After we reported the vulnerability to the vendor and released our blog post, similar security vulnerabilities that base on PHP’s built-in mail() function popped up in other PHP applications 1 2 3 4. In this post, we have a look at the common ground of these vulnerabilities, which security patches are faulty, and how to use mail() securely.

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Roundcube 1.2.2: Command Execution via Email

6 Dec 2016 by Robin Peraglie

Roundcube

Roundcube is a widely distributed open-source webmail software used by many organizations and companies around the globe. The mirror on SourceForge, for example, counts more than 260,000 downloads in the last 12 months1 which is only a small fraction of the actual users. Once Roundcube is installed on a server, it provides a web interface for authenticated users to send and receive emails with their web browser.

In this post, we show how a malicious user can remotely execute arbitrary commands on the underlying operating system, simply by writing an email in Roundcube 1.2.2 (>= 1.0). This vulnerability is highly critical because all default installations are affected. We urge all administrators to update the Roundcube installation to the latest version 1.2.3 as soon as possible.

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