The shipped “secure” security policy includes a rule intended to prevent reading/writing from standard streams:
<policy domain="path" rights="none" pattern="-"/>
However, ImageMagick also supports fd:<n> pseudo-filenames (e.g., fd:0, fd:1). This path form is not blocked by the secure policy templates, and therefore bypasses the protection goal of “no stdin/stdout”.
To resolve this, users can add the following change to their security policy.
<policy domain="path" rights="none" pattern="fd:*"/>
And this will also be included in ImageMagick's more secure policies by default.
NVD description
ImageMagick is free and open-source software used for editing and manipulating digital images. The shipped "secure" security policy includes a rule intended to prevent reading/writing from standard streams. However, ImageMagick also supports fd:<n> pseudo-filenames (e.g., fd:0, fd:1). Prior to versions 7.1.2-15 and 6.9.13-40, this path form is not blocked by the secure policy templates, and therefore bypasses the protection goal of "no stdin/stdout." Versions 7.1.2-15 and 6.9.13-40 contain a patch by including a change to the more secure policies by default. As a workaround, add the change to one's security policy manually.