Hypermail SSI Vulnerability
qDefense Advisory Number QDAV-2001-11-1

Product: Hypermail

Vendor: Hypermail Development (http://www.hypermail.org)

Severity: Remote; Attacker may be able to execute arbitrary commands on servers that run Hypermail and SSI

Vendor Status: Vendor contacted; patch released

In Short: Hypermail can be used to create arbitrary files, with arbitrary extensions, on the server, which may then possibly be used to execute SSI commands.

The current version of this document is available at http://qDefense.com/Advisories/QDAV-2001-11-1.html.


Hypermail converts e-mails into HTML. It is generally used to automatically create web archives of mailing lists. When e-mails are archived, attachments which are included are archived as well. The attachments are not modified before archival, and they are stored under the filename contained in the e-mail.

An attacker can therefore create an arbitrary file on the web server with an arbitrary extension. If the server supports SSI, an attacker can include SSI commands in a file, give it the SSI extension (normally .shtml), and mail it. This will create the desired file on the server. The attacker can than cause the server to execute those SSI commands by requesting the attachment.

It should be noted that creation of arbitrary files on a web server carries with it additional insecurites besides SSI, and therefore even servers that do not support SSI may be vulnerable.


Hypermail has been patched to convert .shtml extensions to .html. As of this writing, no further correction has been taken.

Servers should never allow SSI, CGI, or any other type of server processed content in the hypermail directory.

© 2001 qDefense Penetration Testing. qDefense Penetration Testing is a subsidiary of Computer Modeling Corp.

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