Affected: Erlang OTP

Server-Side Request Forgery (SSRF) vulnerability in Erlang/OTP ftp (ftp_internal module) allows FTP bounce attacks and SSRF via an unvalidated PASV response IP address.

The ftp_internal:handle_ctrl_result/2 PASV handler (mode=passive, ipfamily=inet, ftp_extension=false) extracts the IP address from the server's 227 response and passes it directly to gen_tcp:connect/4 without validating it against the control connection peer address. The adjacent EPSV handlers correctly call peername(CSock) to derive the IP from the control connection, but the PASV handler does not. A malicious or compromised FTP server can redirect the client's data connection to an arbitrary internal host and port. On read operations (ftp:ls/1,2, ftp:nlist/1,2, ftp:recv/2,3), data from the redirected target is returned to the caller. On write operations (ftp:send/2,3, ftp:append/2,3), file content is sent to the redirected target. This enables SSRF against internal hosts, cloud metadata endpoints, and FTP bounce attacks against third-party hosts.

The vulnerable path is the default configuration (mode=passive, ipfamily=inet, ftp_extension=false). RFC 2577 section 3 explicitly recommends validating the PASV response IP against the control connection peer.

The ftp application is deprecated and scheduled for removal in OTP-30.

This vulnerability is associated with program files lib/inets/src/ftp/ftp_internal.erl (inets 5.10.4 through 6.5, OTP 17.4 through 20.3) and lib/ftp/src/ftp_internal.erl (ftp 1.0 and…