CVE-2026-2708

A request smuggling vulnerability exists in libsoup's HTTP/1 header parsing logic. The soup_message_headers_append_common() function in libsoup/soup-message-headers.c unconditionally appends each header value without validating for duplicate or conflicting Content-Length fields. This allows an attacker to send HTTP requests containing multiple Content-Length headers with differing values.

The practical impact is limited because SoupServer is a testing and development utility, not designed for production internet infrastructure. Exploitation requires a deployment topology where SoupServer is serving real traffic behind (or in front of) another HTTP server acting as a proxy — a scenario that contradicts its intended use.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.