As you know, thttpd, unlike dhttpd, supports CGI but the man page does not refer to the HTTP level supported for the requests in the documentation. From the thttpd man page:
thttpd supports the CGI 1.1 spec.
In order for a CGI program to be run, its name must match the pattern
specified either at compile time or on the command line with the -c
flag. This is a simple shell-style filename pattern. You can use * to
match any string not including a slash, or ** to match any string
including slashes, or ? to match any single character. You can also
use multiple such patterns separated by |. The patterns get checked
against the filename part of the incoming URL. Don’t forget to quote
any wildcard characters so that the shell doesn’t mess with them.
Restricting CGI programs to a single directory lets the site adminis‐
trator review them for security holes, and is strongly recommended. If
there are individual users that you trust, you can enable their direc‐
If no CGI pattern is specified, neither here nor at compile time, then
CGI programs cannot be run at all. If you want to disable CGI as a
security measure, that’s how you do it, just comment out the patterns
in the config file and don’t run with the -c flag.
Note: the current working directory when a CGI program gets run is the
directory that the CGI program lives in. This isn’t in the CGI 1.1
spec, but it’s what most other HTTP servers do.
Relevant config.h options: CGI_PATTERN, CGI_TIMELIMIT, CGI_NICE,
CGI_PATH, CGI_LD_LIBRARY_PATH, CGIBINDIR.
On the specific question of HTTP 1.1 support, I think asking on the thttpd support forum was probably the best way forward, short of reading the code. I would not be surprised at HTTP 1.0 only as it saves the server having to store pieces of the page until the whole page is available in order to fill in the byte count correctly in the HTTP 1.1 header.
Certainly in the routine
cgi_interpose_output( httpd_conn* hc, int rfd ) in libhttpd.c
the sequence starting
(void) my_snprintf( buf, sizeof(buf), "HTTP/1.0 %d %s\015\012", status, title );
seems to support this view but I expect you are probably more familiar with the code than I am and there will be folk on the mailing list who know it in detail and could be more definitive.