SSH through HTTP proxy with corkscrew

I'm running into an issue connecting from a Cygwin terminal to my home Raspberry Pi with SSH from behind an HTTP proxy. It used-to-work™ and I don't know what changed since a few days ago (maybe the proxy filtering?). I can still connect from outside the proxy-ed network without corkscrew. Client-wise, my ssh-config is as follows: Host * ServerAliveInterval 60 ProxyCommand /bin/corkscrew http.proxy.here 80 %h %p And the connection attempt gives this: blx@proxyed-pc:~$ ssh blx@my.home.ip -v OpenSSH_7.9p1, OpenSSL 1.0.2p 14 Aug 2018 debug1: Reading configuration data /home/blx/.ssh/config debug1: /home/blx/.ssh/config line 1: Applying options for * debug1: Executing proxy command: exec /bin/corkscrew http.proxy.here 80 my.home.ip 22 debug1: identity file /home/blx/.ssh/id_rsa type -1 debug1: identity file /home/blx/.ssh/id_rsa-cert type -1 debug1: identity file /home/blx/.ssh/id_dsa type -1 debug1: identity file /home/blx/.ssh/id_dsa-cert type -1 debug1: identity file /home/blx/.ssh/id_ecdsa type 2 debug1: identity file /home/blx/.ssh/id_ecdsa-cert type -1 debug1: identity file /home/blx/.ssh/id_ed25519 type -1 debug1: identity file /home/blx/.ssh/id_ed25519-cert type -1 debug1: identity file /home/blx/.ssh/id_xmss type -1 debug1: identity file /home/blx/.ssh/id_xmss-cert type -1 debug1: Local version string SSH-2.0-OpenSSH_7.9 ssh_exchange_identification: Connection closed by remote host Server-wise, /var/log/auth reports this: Nov 26 13: 39:36 raspi sshd: debug1: Forked child 19699. Nov 26 13: 39:36 raspi sshd: debug1: Set /proc/self/oom_score_adj to 0 Nov 26 13: 39:36 raspi sshd: debug1: rexec start in 5 out 5 newsock 5 pipe 7 sock 8 Nov 26 13: 39:36 raspi sshd: debug1: inetd sockets after dupping: 3, 3 Nov 26 13: 39:36 raspi sshd: debug1: getpeername failed: Transport endpoint is not connected Nov 26 13: 39:36 raspi sshd: debug1: ssh_remote_port failed So the TCP connection seems broken, but I don't seem to have this issue when I try to connect with corkscrew directly (i.e. $corkscrew http.proxy.here 80 my.home.ip 22): Nov 26 13: 39:32 raspi sshd: debug1: Forked child 19698. Nov 26 13: 39:32 raspi sshd: debug1: Set /proc/self/oom_score_adj to 0 Nov 26 13: 39:32 raspi sshd: debug1: rexec start in 5 out 5 newsock 5 pipe 7 sock 8 Nov 26 13: 39:32 raspi sshd: debug1: inetd sockets after dupping: 3, 3 Nov 26 13: 39:32 raspi sshd: Connection from http.proxy.here port 28220 on 192.168.0.11 port 22 Nov 26 13: 39:32 raspi sshd: Did not receive identification string from http.proxy.here port 28220 But then of course sshd doesn't know what to do of this... Any tip? Since I don't think I changed anything in my setup I suspect a sneaky update of the proxy filtering policy that puts me in this situation, but I have no way to be sure. I will try and update my router and Pi to use port 443 when I get home.