Apply by doing:
	cd /usr/src
	patch -p0 < 017_smrsh.patch

And then rebuild and install smrsh:
	cd gnu/usr.sbin/sendmail/libsm
	make obj
	make depend
	make
	cd ../smrsh
	make obj
	make depend
	make
	make install

Index: gnu/usr.sbin/sendmail/smrsh/smrsh.c
===================================================================
RCS file: /cvs/src/gnu/usr.sbin/sendmail/smrsh/smrsh.c,v
retrieving revision 1.8
retrieving revision 1.8.4.1
diff -u -r1.8 -r1.8.4.1
--- gnu/usr.sbin/sendmail/smrsh/smrsh.c	1 Oct 2001 17:18:30 -0000	1.8
+++ gnu/usr.sbin/sendmail/smrsh/smrsh.c	6 Nov 2002 22:07:54 -0000	1.8.4.1
@@ -56,6 +56,8 @@
 #include <sm/io.h>
 #include <sm/string.h>
 #include <sys/file.h>
+#include <sys/types.h>
+#include <sys/stat.h>
 #include <string.h>
 #include <ctype.h>
 #include <errno.h>
@@ -148,6 +150,7 @@
 	char cmdbuf[1000];
 	char pathbuf[1000];
 	char specialbuf[32];
+	struct stat st;
 
 #ifndef DEBUG
 # ifndef LOG_MAIL
@@ -288,6 +291,38 @@
 			(void) sm_io_fprintf(smioout, SM_TIME_DEFAULT,
 					     "Trying %s\n", cmdbuf);
 #endif /* DEBUG */
+			if (stat(cmdbuf, &st) < 0)
+			{
+				/* can't stat it */
+				(void) sm_io_fprintf(smioerr, SM_TIME_DEFAULT,
+						     "%s: %s not available for sendmail programs (stat failed)\n",
+						      prg, cmd);
+				if (p != NULL)
+					*p = ' ';
+#ifndef DEBUG
+				syslog(LOG_CRIT, "uid %d: attempt to use %s (stat failed)",
+				       (int) getuid(), cmd);
+#endif /* ! DEBUG */
+				exit(EX_UNAVAILABLE);
+			}
+			if (!S_ISREG(st.st_mode)
+#ifdef S_ISLNK
+			    && !S_ISLNK(st.st_mode)
+#endif /* S_ISLNK */
+			   )
+			{
+				/* can't stat it */
+				(void) sm_io_fprintf(smioerr, SM_TIME_DEFAULT,
+						     "%s: %s not available for sendmail programs (not a file)\n",
+						      prg, cmd);
+				if (p != NULL)
+					*p = ' ';
+#ifndef DEBUG
+				syslog(LOG_CRIT, "uid %d: attempt to use %s (not a file)",
+				       (int) getuid(), cmd);
+#endif /* ! DEBUG */
+				exit(EX_UNAVAILABLE);
+			}
 			if (access(cmdbuf, X_OK) < 0)
 			{
 				/* oops....  crack attack possiblity */