The TLS driver in ejabberd before 2.1.12 supports (1) SSLv2 and (2) weak SSL ciphers, which makes it easier for remote attackers to obtain sensitive information via a brute-force attack.

expat_erl.c in ejabberd before 2.1.7 and 3.x before 3.0.0-alpha-3, and exmpp before 0.9.7, does not properly detect recursion during entity expansion, which allows remote attackers to cause a denial of service (memory and CPU consumption) via a crafted XML document containing a large number of nested entity references, a similar issue to CVE-2003-1564.

ejabberd_c2s.erl in ejabberd before 2.1.3 allows remote attackers to cause a denial of service (daemon crash) via a large number of c2s (aka client2server) messages that trigger a queue overload.

Cross-site scripting (XSS) vulnerability in ejabberd before 2.0.4 allows remote attackers to inject arbitrary web script or HTML via unknown vectors related to links and MUC logs.

A third-party installer generation tool, possibly BitRock InstallBuilder, as used in products including Process-one ejabberd 1.1.1_1 and earlier, generates an installer that allows local users to cause a denial of service via a symlink attack on the bitrock_installer.log temporary file. NOTE: it is possible that this vulnerability is present in other products that use this installer.