Code injection

OpenSIPS is a Session Initiation Protocol (SIP) server implementation. Prior to versions 3.1.7 and 3.2.4, sending a malformed Via header to OpenSIPS triggers a segmentation fault when the function calc_tag_suffix is called. A specially crafted Via header, which is deemed correct by the parser, will pass uninitialized strings to the function MD5StringArray which leads to the crash. Abuse of this vulnerability leads to Denial of Service due to a crash. Since the uninitialized string points to memory location 0x0, no further exploitation appears to be possible. No special network privileges are required to perform this attack, as long as the OpenSIPS configuration makes use of functions such as sl_send_reply or sl_gen_totag that trigger the vulnerable code. This issue has been fixed in versions 3.1.7 and 3.2.4.