Arch Linux ASA-201509-4 High: OpenLDAP Denial of Service Threat

Arch Linux Security Advisory ASA-201509-4
========================================
Severity: High
Date    : 2015-09-12
CVE-ID  : CVE-2015-6908
Package : openldap
Type    : denial of service
Remote  : Yes
Link    : https://wiki.archlinux.org/title/CVE

Summary
======
The package openldap before version 2.4.42-2 is vulnerable to a remote
denial of service.

Resolution
=========
Upgrade to 2.4.42-2.

# pacman -Syu "openldap>=2.4.42-2"

The problem has been fixed upstream but no release is available yet.

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

Description
==========
By sending a crafted packet, an attacker can cause the OpenLDAP daemon
to crash with a SIGABRT. This is due to an assert() call within the
ber_get_next method (io.c line 682) that is hit when decoding tampered
BER data.
The following proof of concept exploit can be used to trigger the condition:

# echo "/4SEhISEd4MKYj5ZMgAAAC8=" | base64 -d | nc -v 127.0.0.1 389

The above causes slapd to abort as follows when running with '-d3',
however it should be noted that this will crash the server even when
running in daemon mode.

Impact
=====
A remote attacker is able to send specially crafted packets that cause
the OpenLDAP server to crash, leading to denial of service.

References
=========
https://bugs.openldap.org/show_bug.cgi
https://git.openldap.org/users/sign_in
https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2015-6908
https://bugs.archlinux.org/task/46265