CVE-2021-37706

PJSIP is a free and open source multimedia communication library written in
C language implementing standard based protocols such as SIP, SDP, RTP,
STUN, TURN, and ICE. In affected versions if the incoming STUN message
contains an ERROR-CODE attribute, the header length is not checked before
performing a subtraction operation, potentially resulting in an integer
underflow scenario. This issue affects all users that use STUN. A malicious
actor located within the victim’s network may forge and send a specially
crafted UDP (STUN) message that could remotely execute arbitrary code on
the victim’s machine. Users are advised to upgrade as soon as possible.
There are no known workarounds.