GLSA 200408-19: courier-imap: Remote Format String Vulnerability

Title:courier-imap: Remote Format String Vulnerability
Bugs: #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).


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

Affected packages

Package Vulnerable Unaffected Architecture(s)
net-mail/courier-imap <= 3.0.2-r1 >= 3.0.5 All supported architectures


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.


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:

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



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