CVE-2018-7560: AWS Lambda parser is vulnerable to Regular Expression Denial of Service

The vulnerability stems from the line .split(new RegExp(boundary)) in the parse function. The boundary value is extracted directly from the HTTP request headers without sanitization, and converting it to a RegExp object enables ReDoS attacks via malicious boundary patterns. The patch replaces new RegExp(boundary) with a direct string split (split(boundary)), confirming this was the vulnerable code path. The parse function is the entry point for processing untrusted input and directly handles the dangerous regex construction.