PJSIP: SIP message header buffer overflow

PJSIP is a free and open source multimedia communication library written in C. Prior to commit d6a0e7f, a buffer overflow can occur in pjsip_generic_array_hdr_print() in pjsip/src/pjsip/sip_msg.c, the function that serializes generic array headers (such as Allow, Require, Supported, and Unsupported). Under certain output-buffer boundary conditions the function can write one byte past the end of the buffer. This is reachable mainly in applications that parse and re-serialize incoming SIP requests — for example a proxy, SBC, or B2BUA — where a remote peer can influence the serialized message. The out-of-bounds write is a single fixed byte; code execution and information disclosure are not demonstrated, and in typical pool-based allocations the byte falls within allocation slack. This issue has been patched via commit d6a0e7f.