uhttpd vulnerabilities

The web-based management interface uses a modified uhttpd server with CGI shell scripts. The HTTP Basic Authentication username, taken directly from the Authorization header without sanitization, is inserted into a shell command string executed via the system() function. By submitting a specially crafted username containing shell metacharacters, an unauthenticated attacker with network access to the device can escape the command context and execute arbitrary commands with root privileges.

In unpatched uhttpd repository snapshots, `client_parse_header()` compares the `Transfer-Encoding` value to `chunked` case-sensitively, although transfer-coding tokens are case-insensitive. A mixed-case token is accepted without enabling chunked handling, allowing HTTP request smuggling on keep-alive connections.

In unpatched uhttpd repository snapshots, `uh_ubus_data_send()` can desynchronize HTTP request boundaries when a `POST /ubus` JSON body arrives in multiple TCP segments. The unread body suffix is then processed as a new request on the same keep-alive connection.

uhttpd is a small HTTP server. In unpatched repository snapshots, client_poll_post_data() in client.c consumes an invalid chunk-length line (e.g., a size exceeding INT_MAX), then clears r->content_length and r->transfer_chunked without draining the remaining body or setting request.connection_close. Attacker-controlled body bytes aligned as a complete HTTP request are then parsed and processed as another request on the same connection, causing HTTP request smuggling and request-boundary desynchronization.