REDHAT-BUG-605397

First published: Thu Jun 17 2010(Updated: )

Quoting from the upstream bug report <a href="http://cups.org/str.php?L3510">http://cups.org/str.php?L3510</a>: directory that is writable by unprivileged processes. This is a latent privilege escalation vulnerability. It can be exploited only in the presence of other CUPS vulnerabilities. Why this is privilege escalation -------------------------------- This is privilege escalation, because an unprivileged process can trick the CUPS server into overwriting arbitrary files as root. Example: drwxrwxr-x 4 root lp /var/cache/cups -rw-r----- 1 root lp /var/cache/cups/remote.cache This file is opened with cupsFileOpen() which simply opens the file with open(filename, O_WRONLY | O_TRUNC | O_CREAT | O_LARGEFILE | O_BINARY, 0666). If a CUPS "external" program has a vulnerability, an attacker can use the group=lp privileges to replace /var/cache/cups/remote.cache with a symlink to a root-writable file. CUPS will then overwrite that file as root. A similar latent vulnerability exists for the state file /var/cache/cups/job.cache. Why this is a latent vulnerability ---------------------------------- This is a latent vulnerability, because there is no known exploit for CUPS "external" programs that run as user=lp, group=lp. The upstream fix looks more like a preventative fix as there does not seem to be anything exploitable here, so this looks like more a hardening than a response to an actual flaw.

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