FreeSWITCH is an open-source software telecommunications platform. Before version 1.11.2, an integer underflow in  switch_xml_decode()  can cause an undersized heap allocation when an XML document declares an entity with an empty replacement value. Subsequent copying overruns the allocated buffer. An unauthenticated attacker who can reach a SIP profile with presence management enabled and DTD processing permitted can trigger the vulnerability through a crafted SIP PUBLISH request. Exploitation can corrupt heap memory and terminate the FreeSWITCH process, interrupting all active calls. This vulnerability is fixed in version 1.11.2.