The remote host is missing an update to netpbm-free announced via advisory DSA 1021-1. Max Vozeler from the Debian Audit Project discovered that pstopnm, a converter from Postscript to the PBM, PGM and PNM formats, launches Ghostscript in an insecure manner, which might lead to the execution of arbitrary shell commands, when converting specially crafted Postscript files. For the old stable distribution (woody) this problem has been fixed in version 9.20-8.6.
For the stable distribution (sarge) this problem has been fixed in version 10.0-8sarge3. For the unstable distribution (sid) this problem has been fixed in version 10.0-9. We recommend that you upgrade your netpbm package. https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201021-1