PJSIP is a free and open source multimedia communication library written in C. Versions 2.16 and below have a Heap-based Buffer Overflowvulnerability in the DNS parser's name length handler. Thisimpacts applications using PJSIP's built-in DNS resolver, such as those configured with pjsua_config.nameserver or UaConfig.nameserver in PJSUA/PJSUA2.

It does not affect users who rely on the OS resolver (e.g., getaddrinfo()) by not configuring a nameserver, or those using an external resolver via pjsip_resolver_set_ext_resolver(). This issue is fixed in version 2.17. For users unable to upgrade, a workaround is to disable DNS resolution in the PJSIP config (by setting nameserver_count to zero) or to use an external resolver implementation instead.