Arch Linux Security Advisory ASA-201705-1
========================================
Severity: Medium
Date    : 2017-05-01
CVE-ID  : CVE-2017-2669
Package : dovecot
Type    : denial of service
Remote  : Yes
Link    : https://security.archlinux.org/AVG-238

Summary
======
The package dovecot before version 2.2.29.1-1 is vulnerable to denial
of service.

Resolution
=========
Upgrade to 2.2.29.1-1.

# pacman -Syu "dovecot>=2.2.29.1-1"

The problem has been fixed upstream in version 2.2.29.1.

Workaround
=========
None.

Description
==========
A security issue has been found in Dovecot >= 2.2.26 and <= 2.2.28. If
the "dict" passdb is used for authentication, the username sent by the
client is passed to the var_expand() function and double expansion of
%-variables is performed. A remote unauthenticated attacker could then
send a specially crafted username containing %variables to cause a
denial of service.

Impact
=====
A remote, unauthenticated attacker can cause a denial of service by
sending a specially crafted username.

References
=========
https://dovecot.org/list/dovecot-news/2017-April/000341.html
https://github.com/dovecot/core/commit/000030feb7a30f193197f1aab8a7b04a26b42735.patch
https://security.archlinux.org/CVE-2017-2669