CVE-2026-47072

Name of the Vulnerable Software and Affected Versions hackney versions 2.0.0 through 4.0.0

Description Improper Neutralization of CRLF Sequences, also known as CRLF Injection, allows HTTP Request/Response Splitting. The WebSocket upgrade code in src/hackney ws.erl copies the host, path, headers (ExtraHeaders), and protocols options from the caller-supplied opts map into the internal #ws data{} record in init/1 and then splices them verbatim into the raw HTTP/1.1 upgrade request by binary concatenation in do handshake/1. Because no CRLF or NUL stripping is performed at these four injection sites, an attacker controlling these options—such as by forwarding URL components or header values from untrusted input into hackney ws:start link/1—can inject arbitrary HTTP headers into the outbound WebSocket upgrade request. This can lead to header injection, credential spoofing toward the upstream server, log and cache poisoning, or request smuggling via intermediary proxies.

Recommendations Update to version 4.0.1.