netpbm is a graphics conversion toolkit made up of a large number of single-purpose programs. Many of these programs were found to create temporary files in an insecure manner, which could allow a local attacker to overwrite files with the privileges of the user invoking a vulnerable netpbm tool.
For the current stable distribution (woody) these problems have been fixed in version 2:9.20-8.4.
For the unstable distribution (sid) these problems have been fixed in version 2:9.25-9.
We recommend that you update your netpbm-free package.
MD5 checksums of the listed files are available in the original advisory.