The msn_slp_process_msg function in libpurple/protocols/msn/slpcall.c in the MSN protocol plugin in libpurple 2.6.0 and 2.6.1, as used in Pidgin before 2.6.2, allows remote attackers to cause a denial of service (application crash) via a handwritten (aka Ink) message, related to an uninitialized variable and the incorrect "UTF16-LE" charset name.

The msn_slplink_process_msg function in libpurple/protocols/msn/slplink.c in libpurple, as used in Pidgin (formerly Gaim) before 2.5.9 and Adium 1.3.5 and earlier, allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption and application crash) by sending multiple crafted SLP (aka MSNSLP) messages to trigger an overwrite of an arbitrary memory location. NOTE: this issue reportedly exists because of an incomplete fix for CVE-2009-1376.

The OSCAR protocol implementation in Pidgin before 2.5.8 misinterprets the ICQWebMessage message type as the ICQSMS message type, which allows remote attackers to cause a denial of service (application crash) via a crafted ICQ web message that triggers allocation of a large amount of memory.

Buffer overflow in the XMPP SOCKS5 bytestream server in Pidgin (formerly Gaim) before 2.5.6 allows remote authenticated users to execute arbitrary code via vectors involving an outbound XMPP file transfer. NOTE: some of these details are obtained from third party information.

Buffer overflow in the decrypt_out function in Pidgin (formerly Gaim) before 2.5.6 allows remote attackers to cause a denial of service (application crash) via a QQ packet.

The PurpleCircBuffer implementation in Pidgin (formerly Gaim) before 2.5.6 does not properly maintain a certain buffer, which allows remote attackers to cause a denial of service (memory corruption and application crash) via vectors involving the (1) XMPP or (2) Sametime protocol.

Multiple integer overflows in the msn_slplink_process_msg functions in the MSN protocol handler in (1) libpurple/protocols/msn/slplink.c and (2) libpurple/protocols/msnp9/slplink.c in Pidgin (formerly Gaim) before 2.5.6 on 32-bit platforms allow remote attackers to execute arbitrary code via a malformed SLP message with a crafted offset value, leading to buffer overflows. NOTE: this issue exists because of an incomplete fix for CVE-2008-2927.

The NSS plugin in libpurple in Pidgin 2.4.3 does not verify SSL certificates, which makes it easier for remote attackers to trick a user into accepting an invalid server certificate for a spoofed service.