ImageMagick vulnerability

php.internals

Dan Ackroyd

10 years ago
Hello, Sorry for being off-topic, but as the maintainer for the Imagick extension I feel it necessary to do my best impression of Paul Revere* and warn people of an alleged vulnerability in the underlying ImageMagick library. Apparently servers that use ImageMagick to process any user uploaded images are vulnerable to a remote code execution attack. Ways to mitigate this vulnerability are at: https://imagetragick.com/ which include: ####### Verify that all image files begin with the expected "magic bytes" corresponding to the image file types you support before sending them to ImageMagick for processing. Use a policy file to disable the vulnerable ImageMagick coders. The global policy for ImageMagick is usually found in “/etc/ImageMagick”. The below policy.xml example will disable the coders EPHEMERAL, URL, MVG, and MSL. <policymap> <policy domain="coder" rights="none" pattern="EPHEMERAL" /> <policy domain="coder" rights="none" pattern="URL" /> <policy domain="coder" rights="none" pattern="HTTPS" /> <policy domain="coder" rights="none" pattern="MVG" /> <policy domain="coder" rights="none" pattern="MSL" /> </policymap> ####### I believe restarting any PHP process that would have loaded the Imagick extension is required to ensure this mitigation takes effect. For the record, I do not know any more details about the vulnerability. Nor do I believe there are any mitigation step that could or should be taken in the Imagick extension code. As an aside, I do recommend only processing images in a locked down 'background worker' process, rather directly in the web server; I'm not sure if that would help in for this particular vulnerability, but it is usually a good idea. cheers Dan Ack * https://twitter.com/MrDanack/status/727623821860216832

Yasuo Ohgaki

10 years ago
Hi Dan, On Wed, May 4, 2016 at 7:33 AM, Dan Ackroyd <danack@basereality.com> wrote:
> Sorry for being off-topic, but as the maintainer for the Imagick > extension I feel it necessary to do my best impression of Paul Revere* > and warn people of an alleged vulnerability in the underlying > ImageMagick library.
Not at all. Thank you for letting us know! Regards,
-- Yasuo Ohgaki yohgaki@ohgaki.net