NetSaro Enterprise Messenger Server 2.0 stores cleartext console credentials in configuration.xml, which allows local users to obtain sensitive information by reading this file and performing a base64 decoding step.

The Server Administration Console in NetSaro Enterprise Messenger Server 2.0 allows remote attackers to read application source code by appending a %00 character to a URL.

win32k.sys in the kernel-mode drivers in Microsoft Windows XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista SP1 and SP2, Windows Server 2008 Gold, SP2, R2, and R2 SP1, and Windows 7 Gold and SP1 allows local users to gain privileges via a crafted application that triggers a NULL pointer dereference, a different vulnerability than other "Vulnerability Type 2" CVEs listed in MS11-034, aka "Win32k Null Pointer De-reference Vulnerability."

aMSN (aka Alvaro's Messenger) 0.98.3 and earlier, when SSL is used, does not verify that the server hostname matches a domain name in the subject's Common Name (CN) field or a Subject Alternative Name field of the X.509 certificate, which allows man-in-the-middle attackers to spoof an MSN server via an arbitrary certificate.

Stack-based buffer overflow in the AntServer Module (AntServer.exe) in BigAnt IM Server 2.50 allows remote attackers to execute arbitrary code via a long GET request to TCP port 6660.

A certain ActiveX control in msgsc.14.0.8089.726.dll in Microsoft Windows Live Messenger 2009 build 14.0.8089.726 on Windows Vista and Windows 7 allows remote attackers to cause a denial of service (msnmsgr.exe crash) by calling the ViewProfile method with a crafted argument during an MSN Messenger session.

An ActiveX control in YahooBridgeLib.dll for Yahoo! Messenger 9.0.0.2162, and possibly other 9.0 versions, allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) by calling the RegisterMe method with a long argument.

The server in Mitel NuPoint Messenger R11 and R3 sends usernames and passwords in cleartext to Exchange servers, which allows remote attackers to obtain sensitive information by sniffing the network.

msnmsgr.exe in Windows Live Messenger (WLM) 2009 build 14.0.8064.206, and other 14.0.8064.x builds, allows remote attackers to cause a denial of service (application crash) via a modified header in a packet, as possibly demonstrated by a UTF-8.0 value of the charset field in the Content-Type header line. NOTE: this has been reported as a format string vulnerability by some sources, but the provenance of that information is unknown.

Microsoft Windows Live Messenger Client 8.5.1 and earlier, when MSN Protocol Version 15 (MSNP15) is used over a NAT session, allows remote attackers to discover intranet IP addresses and port numbers by reading the (1) IPv4InternalAddrsAndPorts, (2) IPv4Internal-Addrs, and (3) IPv4Internal-Port header fields.