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courier-imap: Remote Format String Vulnerability


1.  Gentoo Linux Security Advisory

Version Information

Advisory Reference GLSA 200408-19 / courier-imap
Release Date August 19, 2004
Latest Revision May 22, 2006: 02
Impact high
Exploitable remote
Package Vulnerable versions Unaffected versions Architecture(s)
net-mail/courier-imap <= 3.0.2-r1 >= 3.0.5 All supported architectures

Related bugreports: #60865


There is a format string vulnerability in non-standard configurations of courier-imapd which may be exploited remotely. An attacker may be able to execute arbitrary code as the user running courier-imapd (oftentimes root).

2.  Impact Information


Courier-IMAP is an IMAP server which is part of the Courier mail system. It provides access only to maildirs.


There is a format string vulnerability in the auth_debug() function which can be exploited remotely, potentially leading to arbitrary code execution as the user running the IMAP daemon (oftentimes root). A remote attacker may send username or password information containing printf() format tokens (such as "%s"), which will crash the server or cause it to execute arbitrary code.

This vulnerability can only be exploited if DEBUG_LOGIN is set to something other than 0 in the imapd config file.


If DEBUG_LOGIN is enabled in the imapd configuration, a remote attacker may execute arbitrary code as the root user.

3.  Resolution Information


Set the DEBUG_LOGIN option in /etc/courier-imap/imapd to 0. (This is the default value.)


All courier-imap users should upgrade to the latest version:

Code Listing 3.1: Resolution

# emerge sync

# emerge -pv ">=net-mail/courier-imap-3.0.5"
# emerge ">=net-mail/courier-imap-3.0.5"

4.  References


Page updated August 19, 2004

Summary: This is a Gentoo Linux Security Advisory

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