OpenSIPS is a Session Initiation Protocol (SIP) server implementation. 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 issue 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.