Stefan Sperling discovered that pidgin-otr, a Pidgin plugin implementing Off-The-Record messaging, contained a use-after-free bug. This could be used by a malicious remote user to intentionally crash the application, thus causing a denial-of-service.
For the stable distribution (jessie), this problem has been fixed in version 4.0.1-1+deb8u1.
For the testing (stretch) and unstable (sid) distributions, this problem has been fixed in version 4.0.2-1.
We recommend that you upgrade your pidgin-otr packages.