CVE-2026-45084: OpenSIPS: Denial of service in presence.handle_publish() from unchecked Content-Type state

OpenSIPS is a Session Initiation Protocol (SIP) server implementation. Versions 3.4.0 through 3.6.5 contain a denial of service vulnerability in the presence module. When the presence module's handlepublish() function processes a SIP PUBLISH request with an Event: presence header and a message body while the configuration option enablespherecheck=1 is set, it invokes the getcontenttype() macro without first calling parsecontenttypehdr(), causing it to dereference uninitialized or NULL Content-Type parsing state and crash. If a Content-Type header is present but unparsed, msg->contenttype->parsed is NULL and is dereferenced as a contentt pointer; if the request lacks a Content-Type header entirely, msg->contenttype itself is NULL, and both cases lead to a crash. A remote attacker can therefore cause a denial of service against an affected instance with a single PUBLISH request over UDP or TCP, using either a valid Content-Type: application/pidf+xml request or one with the header removed, and the vulnerable code path itself does not enforce authentication (though a deployment's routing configuration may require it before this route is reached). The issue has been fixed in version 3.6.6 and 4.0.0-rc1.