Fix CVE-2017-12836:

http://cve.mitre.org/cgi-bin/cvename.cgi?name=2017-12836
https://security-tracker.debian.org/tracker/CVE-2017-12836

Patch adpated from Debian (comments and changelog annotations removed):

https://anonscm.debian.org/cgit/collab-maint/cvs.git/commit/?h=stretch&id=41e077396e35efb6c879951f44c62dd8a1d0f094

From 41e077396e35efb6c879951f44c62dd8a1d0f094 Mon Sep 17 00:00:00 2001
From: mirabilos <m@mirbsd.org>
Date: Sat, 12 Aug 2017 03:17:18 +0200
Subject: Fix CVE-2017-12836 (Closes: #871810) for stretch

---
 debian/changelog |  6 ++++++
 src/rsh-client.c | 10 ++++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/rsh-client.c b/src/rsh-client.c
index fe0cfc4..1fc860d 100644
--- a/src/rsh-client.c
+++ b/src/rsh-client.c
@@ -105,6 +106,9 @@ start_rsh_server (cvsroot_t *root, struct buffer **to_server_p,
 	rsh_argv[i++] = argvport;
     }
 
+    /* Only non-option arguments from here. (CVE-2017-12836) */
+    rsh_argv[i++] = "--";
+
     rsh_argv[i++] = root->hostname;
     rsh_argv[i++] = cvs_server;
     if (readonlyfs)
@@ -189,6 +193,8 @@ start_rsh_server (cvsroot_t *root, struct buffer **to_server_p,
 		*p++ = argvport;
 	}
 
+	*p++ = "--";
+
 	*p++ = root->hostname;
 	*p++ = command;
 	*p++ = NULL;
-- 
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