HTTPX2 is a next generation HTTP client for Python. Prior to 2.11.0, FileField.renderheaders() in src/httpx2/httpx2/multipart.py directly interpolates attacker-controlled contenttype values and custom headers from the files= three-element (filename, content, contenttype) tuple and the files= four-element (filename, content, contenttype, headers) tuple into multipart/form-data part headers without validating header names or values. CR or LF characters can terminate a part header, inject additional part headers, or end the part header block early, allowing a downstream multipart parser to treat attacker-supplied lines as genuine headers and potentially alter part semantics or bypass header-based checks. This issue is fixed in version 2.11.0.