Fix a memory exhaustion bug in the key exchange, whereby an unauthenticated user could potentially consume 38400 MB of memory on the server: http://seclists.org/oss-sec/2016/q4/185 Patch adapted from upstream source repository: https://github.com/openssh/openssh-portable/commit/ec165c392ca54317dbe3064a8c200de6531e89ad From ec165c392ca54317dbe3064a8c200de6531e89ad Mon Sep 17 00:00:00 2001 From: "markus@openbsd.org" <markus@openbsd.org> Date: Mon, 10 Oct 2016 19:28:48 +0000 Subject: [PATCH] upstream commit Unregister the KEXINIT handler after message has been received. Otherwise an unauthenticated peer can repeat the KEXINIT and cause allocation of up to 128MB -- until the connection is closed. Reported by shilei-c at 360.cn Upstream-ID: 43649ae12a27ef94290db16d1a98294588b75c05 --- kex.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kex.c b/kex.c index 3f97f8c..6a94bc5 100644 --- a/kex.c +++ b/kex.c @@ -481,6 +481,7 @@ kex_input_kexinit(int type, u_int32_t seq, void *ctxt) if (kex == NULL) return SSH_ERR_INVALID_ARGUMENT; + ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, NULL); ptr = sshpkt_ptr(ssh, &dlen); if ((r = sshbuf_put(kex->peer, ptr, dlen)) != 0) return r; -- 2.10.1