diff --git a/SOURCES/sudo-1.8.31-CVE-2021-3156.patch b/SOURCES/sudo-1.8.31-CVE-2021-3156.patch
new file mode 100644
index 0000000..ba63838
--- /dev/null
+++ b/SOURCES/sudo-1.8.31-CVE-2021-3156.patch
@@ -0,0 +1,207 @@
+diff -up ./plugins/sudoers/policy.c.heap-buffer ./plugins/sudoers/policy.c
+--- ./plugins/sudoers/policy.c.heap-buffer	2021-01-20 13:10:29.368619293 +0100
++++ ./plugins/sudoers/policy.c	2021-01-20 15:56:12.915095745 +0100
+@@ -93,11 +93,12 @@ parse_bool(const char *line, int varlen,
+ int
+ sudoers_policy_deserialize_info(void *v, char **runas_user, char **runas_group)
+ {
++    const int edit_mask = MODE_EDIT|MODE_IGNORE_TICKET|MODE_NONINTERACTIVE;
+     struct sudoers_policy_open_info *info = v;
+-    char * const *cur;
+     const char *p, *errstr, *groups = NULL;
+     const char *remhost = NULL;
+     bool uid_set = false, gid_set = false;
++    char * const *cur;
+     int flags = 0;
+     debug_decl(sudoers_policy_deserialize_info, SUDOERS_DEBUG_PLUGIN)
+ 
+@@ -326,6 +327,12 @@ sudoers_policy_deserialize_info(void *v,
+ #endif
+     }
+ 
++    /* Sudo front-end should restrict mode flags for sudoedit. */
++    if (ISSET(flags, MODE_EDIT) && (flags & edit_mask) != flags) {
++        sudo_warnx(U_("invalid mode flags from sudo front end: 0x%x"), flags);
++        goto bad;
++    }
++
+     user_umask = (mode_t)-1;
+     for (cur = info->user_info; *cur != NULL; cur++) {
+ 	if (MATCHES(*cur, "user=")) {
+diff -up ./plugins/sudoers/sudoers.c.heap-buffer ./plugins/sudoers/sudoers.c
+--- ./plugins/sudoers/sudoers.c.heap-buffer	2021-01-20 13:10:29.350619537 +0100
++++ ./plugins/sudoers/sudoers.c	2021-01-20 13:10:29.369619280 +0100
+@@ -416,7 +416,7 @@ sudoers_policy_main(int argc, char * con
+ 
+     /* If run as root with SUDO_USER set, set sudo_user.pw to that user. */
+     /* XXX - causes confusion when root is not listed in sudoers */
+-    if (sudo_mode & (MODE_RUN | MODE_EDIT) && prev_user != NULL) {
++    if (ISSET(sudo_mode, MODE_RUN|MODE_EDIT) && prev_user != NULL) {
+ 	if (user_uid == 0 && strcmp(prev_user, "root") != 0) {
+ 	    struct passwd *pw;
+ 
+@@ -796,8 +796,8 @@ set_cmnd(void)
+     if (user_cmnd == NULL)
+ 	user_cmnd = NewArgv[0];
+ 
+-    if (sudo_mode & (MODE_RUN | MODE_EDIT | MODE_CHECK)) {
+-	if (ISSET(sudo_mode, MODE_RUN | MODE_CHECK)) {
++    if (ISSET(sudo_mode, MODE_RUN|MODE_EDIT|MODE_CHECK)) {
++	if (!ISSET(sudo_mode, MODE_EDIT)) {
+ 	    if (def_secure_path && !user_is_exempt())
+ 		path = def_secure_path;
+ 	    if (!set_perms(PERM_RUNAS))
+@@ -835,7 +835,8 @@ set_cmnd(void)
+ 		sudo_warnx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+ 		debug_return_int(-1);
+ 	    }
+-	    if (ISSET(sudo_mode, MODE_SHELL|MODE_LOGIN_SHELL)) {
++	    if (ISSET(sudo_mode, MODE_SHELL|MODE_LOGIN_SHELL) &&
++            ISSET(sudo_mode, MODE_RUN)) {
+ 		/*
+ 		 * When running a command via a shell, the sudo front-end
+ 		 * escapes potential meta chars.  We unescape non-spaces
+@@ -843,10 +844,22 @@ set_cmnd(void)
+ 		 */
+ 		for (to = user_args, av = NewArgv + 1; (from = *av); av++) {
+ 		    while (*from) {
+-			if (from[0] == '\\' && !isspace((unsigned char)from[1]))
++			if (from[0] == '\\' && from[1] != '\0' &&
++				!isspace((unsigned char)from[1])) {
+ 			    from++;
++			}
++			if (size - (to - user_args) < 1) {
++			    sudo_warnx(U_("internal error, %s overflow"),
++				__func__);
++			    debug_return_int(NOT_FOUND_ERROR);
++			}
+ 			*to++ = *from++;
+ 		    }
++		    if (size - (to - user_args) < 1) {
++			sudo_warnx(U_("internal error, %s overflow"),
++			    __func__);
++			debug_return_int(NOT_FOUND_ERROR);
++		    }
+ 		    *to++ = ' ';
+ 		}
+ 		*--to = '\0';
+diff -up ./plugins/sudoers/timestamp.c.heap-buffer ./plugins/sudoers/timestamp.c
+--- ./plugins/sudoers/timestamp.c.heap-buffer	2018-09-02 14:30:08.000000000 +0200
++++ ./plugins/sudoers/timestamp.c	2021-01-20 13:10:29.369619280 +0100
+@@ -646,8 +646,8 @@ timestamp_lock(void *vcookie, struct pas
+     } else if (entry.type != TS_LOCKEXCL) {
+ 	/* Old sudo record, convert it to TS_LOCKEXCL. */
+ 	entry.type = TS_LOCKEXCL;
+-	memset((char *)&entry + offsetof(struct timestamp_entry, type), 0,
+-	    nread - offsetof(struct timestamp_entry, type));
++	memset((char *)&entry + offsetof(struct timestamp_entry, flags), 0,
++	    nread - offsetof(struct timestamp_entry, flags));
+ 	if (ts_write(cookie->fd, cookie->fname, &entry, 0) == -1)
+ 	    debug_return_bool(false);
+     }
+diff -up ./src/parse_args.c.heap-buffer ./src/parse_args.c
+--- ./src/parse_args.c.heap-buffer	2018-08-18 16:10:25.000000000 +0200
++++ ./src/parse_args.c	2021-01-20 16:01:42.500778441 +0100
+@@ -116,7 +116,10 @@ struct environment {
+ /*
+  * Default flags allowed when running a command.
+  */
+-#define DEFAULT_VALID_FLAGS	(MODE_BACKGROUND|MODE_PRESERVE_ENV|MODE_RESET_HOME|MODE_LOGIN_SHELL|MODE_NONINTERACTIVE|MODE_SHELL)
++#define DEFAULT_VALID_FLAGS	(MODE_BACKGROUND|MODE_PRESERVE_ENV|MODE_RESET_HOME|MODE_LOGIN_SHELL|MODE_NONINTERACTIVE|MODE_PRESERVE_GROUPS|MODE_SHELL)
++#define EDIT_VALID_FLAGS	MODE_NONINTERACTIVE
++#define LIST_VALID_FLAGS	(MODE_NONINTERACTIVE|MODE_LONG_LIST)
++#define VALIDATE_VALID_FLAGS	MODE_NONINTERACTIVE
+ 
+ /* Option number for the --host long option due to ambiguity of the -h flag. */
+ #define OPT_HOSTNAME	256
+@@ -260,6 +263,7 @@ parse_args(int argc, char **argv, int *n
+ 	progname = "sudoedit";
+ 	mode = MODE_EDIT;
+ 	sudo_settings[ARG_SUDOEDIT].value = "true";
++	valid_flags = EDIT_VALID_FLAGS;
+     }
+ 
+     /* Load local IP addresses and masks. */
+@@ -345,7 +349,7 @@ parse_args(int argc, char **argv, int *n
+ 			usage_excl(1);
+ 		    mode = MODE_EDIT;
+ 		    sudo_settings[ARG_SUDOEDIT].value = "true";
+-		    valid_flags = MODE_NONINTERACTIVE;
++		    valid_flags = EDIT_VALID_FLAGS;
+ 		    break;
+ 		case 'g':
+ 		    if (*optarg == '\0')
+@@ -355,6 +359,7 @@ parse_args(int argc, char **argv, int *n
+ 		    break;
+ 		case 'H':
+ 		    sudo_settings[ARG_SET_HOME].value = "true";
++		    SET(flags, MODE_RESET_HOME);
+ 		    break;
+ 		case 'h':
+ 		    if (optarg == NULL) {
+@@ -404,7 +409,7 @@ parse_args(int argc, char **argv, int *n
+ 			    usage_excl(1);
+ 		    }
+ 		    mode = MODE_LIST;
+-		    valid_flags = MODE_NONINTERACTIVE|MODE_LONG_LIST;
++		    valid_flags = LIST_VALID_FLAGS;
+ 		    break;
+ 		case 'n':
+ 		    SET(flags, MODE_NONINTERACTIVE);
+@@ -412,6 +417,7 @@ parse_args(int argc, char **argv, int *n
+ 		    break;
+ 		case 'P':
+ 		    sudo_settings[ARG_PRESERVE_GROUPS].value = "true";
++		    SET(flags, MODE_PRESERVE_GROUPS);
+ 		    break;
+ 		case 'p':
+ 		    /* An empty prompt is allowed. */
+@@ -455,7 +461,7 @@ parse_args(int argc, char **argv, int *n
+ 		    if (mode && mode != MODE_VALIDATE)
+ 			usage_excl(1);
+ 		    mode = MODE_VALIDATE;
+-		    valid_flags = MODE_NONINTERACTIVE;
++		    valid_flags = VALIDATE_VALID_FLAGS;
+ 		    break;
+ 		case 'V':
+ 		    if (mode && mode != MODE_VERSION)
+@@ -482,7 +488,7 @@ parse_args(int argc, char **argv, int *n
+     if (!mode) {
+ 	/* Defer -k mode setting until we know whether it is a flag or not */
+ 	if (sudo_settings[ARG_IGNORE_TICKET].value != NULL) {
+-	    if (argc == 0 && !(flags & (MODE_SHELL|MODE_LOGIN_SHELL))) {
++	    if (argc == 0 && !ISSET(flags, MODE_SHELL|MODE_LOGIN_SHELL)) {
+ 		mode = MODE_INVALIDATE;	/* -k by itself */
+ 		sudo_settings[ARG_IGNORE_TICKET].value = NULL;
+ 		valid_flags = 0;
+@@ -545,23 +551,24 @@ parse_args(int argc, char **argv, int *n
+     /*
+      * For shell mode we need to rewrite argv
+      */
+-    if (ISSET(mode, MODE_RUN) && ISSET(flags, MODE_SHELL)) {
++    if (ISSET(flags, MODE_SHELL|MODE_LOGIN_SHELL) && ISSET(mode, MODE_RUN)) {
+ 	char **av, *cmnd = NULL;
+ 	int ac = 1;
+ 
+ 	if (argc != 0) {
+ 	    /* shell -c "command" */
+ 	    char *src, *dst;
+-	    size_t cmnd_size = (size_t) (argv[argc - 1] - argv[0]) +
+-		strlen(argv[argc - 1]) + 1;
++        size_t size = 0;
+ 
+-	    cmnd = dst = reallocarray(NULL, cmnd_size, 2);
+-	    if (cmnd == NULL)
++        for (av = argv; *av != NULL; av++)
++            size += strlen(*av) + 1;
++
++        if (size == 0 || (cmnd = reallocarray(NULL, size, 2)) == NULL)
+ 		sudo_fatalx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
+ 	    if (!gc_add(GC_PTR, cmnd))
+ 		exit(1);
+ 
+-	    for (av = argv; *av != NULL; av++) {
++        for (dst = cmnd, av = argv; *av != NULL; av++) {
+ 		for (src = *av; *src != '\0'; src++) {
+ 		    /* quote potential meta characters */
+ 		    if (!isalnum((unsigned char)*src) && *src != '_' && *src != '-' && *src != '$')
diff --git a/SPECS/sudo.spec b/SPECS/sudo.spec
index 7dfc84d..a9d8e28 100644
--- a/SPECS/sudo.spec
+++ b/SPECS/sudo.spec
@@ -1,7 +1,7 @@
 Summary: Allows restricted root access for specified users
 Name: sudo
 Version: 1.8.23
-Release: 10%{?dist}
+Release: 10%{?dist}.1
 License: ISC
 Group: Applications/System
 URL: http://www.courtesan.com/sudo/
@@ -74,6 +74,9 @@ Patch16: sudo-1.8.29-CVE-2019-18634-part2.patch
 Patch17: sudo-1.8.29-expired-password-part1.patch
 Patch18: sudo-1.8.29-expired-password-part2.patch
 
+# 1917729 - EMBARGOED CVE-2021-3156 sudo: Heap-buffer overflow in argument parsing [rhel-7.9.z]
+Patch19: sudo-1.8.31-CVE-2021-3156.patch
+
 %description
 Sudo (superuser do) allows a system administrator to give certain
 users (or groups of users) the ability to run some (or all) commands
@@ -121,6 +124,8 @@ plugins that use %{name}.
 %patch17 -p1 -b .expired-password-part1
 %patch18 -p1 -b .expired-password-part2
 
+%patch19 -p1 -b .heap-buffer
+
 %build
 autoreconf -I m4 -fv --install
 
@@ -256,6 +261,11 @@ rm -rf %{buildroot}
 %{_mandir}/man8/sudo_plugin.8*
 
 %changelog
+* Wed Jan 20 2021 Radovan Sroka <rsroka@redhat.com> - 1.8.23-10.1
+- RHEL 7.9.Z ERRATUM
+- CVE-2021-3156
+Resolves: rhbz#1917729
+
 * Wed Mar 25 2020 Radovan Sroka <rsroka@redhat.com> - 1.8.23-10
 - RHEL-7.9
 - sudo allows privilege escalation with expire password