diff --git a/etc/firejail.config b/etc/firejail.config
index d34bb97be..330cc3b54 100644
--- a/etc/firejail.config
+++ b/etc/firejail.config
@@ -48,6 +48,18 @@
 # cannot be overridden by --noblacklist or --ignore.
 # disable-mnt no
 
+# Maximum number of environment variables.
+# This limit is intended to make stack smashing harder (see
+# https://github.com/netblue30/firejail/issues/4633).
+# env-max-count 256
+
+# Maximum length for each environment variable value.
+# Example: `FOO=barr` has a length of 4.
+# This limit is intended to make stack smashing harder (see
+# https://github.com/netblue30/firejail/issues/4633).
+# Note: The actual default value is based on `PATH_MAX`; see checkcfg.c.
+# env-max-len 4096
+
 # Enable or disable file transfer support, default enabled.
 # file-transfer yes
 
diff --git a/src/firejail/checkcfg.c b/src/firejail/checkcfg.c
index 35030cf99..f270d1a9a 100644
--- a/src/firejail/checkcfg.c
+++ b/src/firejail/checkcfg.c
@@ -36,6 +36,8 @@ char *xvfb_extra_params = "";
 char *netfilter_default = NULL;
 int arg_max_count = 128; // maximum number of command arguments (argc)
 unsigned long arg_max_len = 4096; // --foobar=PATH
+int env_max_count = 256; // some sane maximum number of environment variables
+unsigned long env_max_len = (PATH_MAX + 32); // FOOBAR=SOME_PATH, only applied to Firejail's own sandboxed apps
 unsigned long join_timeout = 5000000; // microseconds
 char *config_seccomp_error_action_str = "EPERM";
 char *config_seccomp_filter_add = NULL;
@@ -239,6 +241,25 @@ int checkcfg(int val) {
 			else if (strncmp(ptr, "arg-max-len ", 12) == 0)
 				arg_max_len = strtoul(ptr + 12, NULL, 10);
 
+			// env max count
+			else if (strncmp(ptr, "env-max-count ", 14) == 0) {
+				long tmp = strtol(ptr + 14, NULL, 10);
+				if (tmp < 0 || tmp >= INT_MAX) {
+					if (arg_debug) {
+						printf("env-max-count out of range: %ld, using %d\n",
+						       tmp, INT_MAX);
+					}
+					env_max_count = INT_MAX;
+				}
+				else {
+					env_max_count = (int)tmp;
+				}
+			}
+
+			// env max len
+			else if (strncmp(ptr, "env-max-len ", 12) == 0)
+				env_max_len = strtoul(ptr + 12, NULL, 10);
+
 			// arp probes
 			else if (strncmp(ptr, "arp-probes ", 11) == 0) {
 				int arp_probes = atoi(ptr + 11);
diff --git a/src/firejail/env.c b/src/firejail/env.c
index 4489ad0c2..f1e1f5d41 100644
--- a/src/firejail/env.c
+++ b/src/firejail/env.c
@@ -283,8 +283,9 @@ static void env_apply_list(const char * const *list, unsigned int num_items) {
 			for (i = 0; i < num_items; i++)
 				if (strcmp(env->name, list[i]) == 0) {
 					// sanity check for whitelisted environment variables
-					if (strlen(env->name) + strlen(env->value) >= MAX_ENV_LEN) {
-						fprintf(stderr, "Error: too long environment variable %s, please use --rmenv\n", env->name);
+					if (strlen(env->name) + strlen(env->value) >= env_max_len) {
+						fprintf(stderr, "Error: too long environment variable value: '%s' len (%zu) >= env-max-len (%lu): '%s'; see --rmenv\n",
+						        env->name, strlen(env->value), env_max_len, env->value);
 						exit(1);
 					}
 
diff --git a/src/firejail/firejail.h b/src/firejail/firejail.h
index e4c155cd4..0f869df91 100644
--- a/src/firejail/firejail.h
+++ b/src/firejail/firejail.h
@@ -739,8 +739,6 @@ int check_namespace_virt(void);
 int check_kernel_procs(void);
 void run_no_sandbox(int argc, char **argv) __attribute__((noreturn));
 
-#define MAX_ENVS 256			// some sane maximum number of environment variables
-#define MAX_ENV_LEN (PATH_MAX + 32)	// FOOBAR=SOME_PATH, only applied to Firejail's own sandboxed apps
 // env.c
 typedef enum {
 	SETENV = 0,
@@ -879,6 +877,8 @@ extern char *xvfb_extra_params;
 extern char *netfilter_default;
 extern int arg_max_count;
 extern unsigned long arg_max_len;
+extern int env_max_count;
+extern unsigned long env_max_len;
 extern unsigned long join_timeout;
 extern char *config_seccomp_error_action_str;
 extern char *config_seccomp_filter_add;
diff --git a/src/firejail/main.c b/src/firejail/main.c
index 56ac19c82..ad022d4d9 100644
--- a/src/firejail/main.c
+++ b/src/firejail/main.c
@@ -1075,7 +1075,7 @@ int main(int argc, char **argv, char **envp) {
 	// check standard streams before opening any file
 	fix_std_streams();
 
-	// initialize values from firejail.config (needed for arg_max_count)
+	// initialize values from firejail.config (needed for arg/env checks)
 	checkcfg(0);
 
 	// argument count should be larger than 0
@@ -1098,12 +1098,13 @@ int main(int argc, char **argv, char **envp) {
 	}
 
 	// Stash environment variables
-	for (i = 0, ptr = envp; ptr && *ptr && i < MAX_ENVS; i++, ptr++)
+	for (i = 0, ptr = envp; ptr && *ptr && i < env_max_count; i++, ptr++)
 		env_store(*ptr, SETENV);
 
 	// sanity check for environment variables
-	if (i >= MAX_ENVS) {
-		fprintf(stderr, "Error: too many environment variables: >= MAX_ENVS (%d)\n", MAX_ENVS);
+	if (i >= env_max_count) {
+		fprintf(stderr, "Error: too many environment variables: >= env-max-count (%d)\n",
+		        env_max_count);
 		exit(1);
 	}