diff --git a/lib/luks2/luks2_json_metadata.c b/lib/luks2/luks2_json_metadata.c
index e346067..f86e8be 100644
--- a/lib/luks2/luks2_json_metadata.c
+++ b/lib/luks2/luks2_json_metadata.c
@@ -594,9 +594,9 @@ static bool validate_segment_intervals(struct crypt_device *cd,
 static int hdr_validate_segments(struct crypt_device *cd, json_object *hdr_jobj)
 {
 	json_object *jobj_segments, *jobj_digests, *jobj_offset, *jobj_size, *jobj_type, *jobj_flags, *jobj;
-	struct interval *intervals;
 	uint64_t offset, size;
 	int i, r, count, first_backup = -1;
+	struct interval *intervals = NULL;
 
 	if (!json_object_object_get_ex(hdr_jobj, "segments", &jobj_segments)) {
 		log_dbg(cd, "Missing segments section.");
@@ -676,10 +676,18 @@ static int hdr_validate_segments(struct crypt_device *cd, json_object *hdr_jobj)
 		return 1;
 	}
 
+	/* avoid needlessly large allocation when first backup segment is invalid */
+	if (first_backup >= count) {
+		log_dbg(cd, "Gap between last regular segment and backup segment at key %d.", first_backup);
+		return 1;
+	}
+
 	if (first_backup < 0)
 		first_backup = count;
 
-	intervals = malloc(first_backup * sizeof(*intervals));
+	if ((size_t)first_backup < SIZE_MAX / sizeof(*intervals))
+		intervals = malloc(first_backup * sizeof(*intervals));
+
 	if (!intervals) {
 		log_dbg(cd, "Not enough memory.");
 		return 1;
diff --git a/tests/generators/generate-luks2-segment-wrong-backup-key-0.img.sh b/tests/generators/generate-luks2-segment-wrong-backup-key-0.img.sh
new file mode 100755
index 0000000..2499a5e
--- /dev/null
+++ b/tests/generators/generate-luks2-segment-wrong-backup-key-0.img.sh
@@ -0,0 +1,67 @@
+#!/bin/bash
+
+. lib.sh
+
+#
+# *** Description ***
+#
+# generate primary header with wrong backup segment id
+#
+# secondary header is corrupted on purpose as well
+#
+
+# $1 full target dir
+# $2 full source luks2 image
+
+function prepare()
+{
+	cp $SRC_IMG $TGT_IMG
+	test -d $TMPDIR || mkdir $TMPDIR
+	read_luks2_json0 $TGT_IMG $TMPDIR/json0
+	read_luks2_bin_hdr0 $TGT_IMG $TMPDIR/hdr0
+	read_luks2_bin_hdr1 $TGT_IMG $TMPDIR/hdr1
+}
+
+function generate()
+{
+	# create illegal backup segment key (used to be bug in 32bit implementations)
+	json_str=$(jq -c '.segments[(.segments | length + 1 | tostring)] = { "type" : "linear", "offset" : "512", "size" : "512", "flags":["backup-x"]}' $TMPDIR/json0)
+	test ${#json_str} -lt $((LUKS2_JSON_SIZE*512)) || exit 2
+
+	write_luks2_json "$json_str" $TMPDIR/json0
+
+	merge_bin_hdr_with_json $TMPDIR/hdr0 $TMPDIR/json0 $TMPDIR/area0
+	erase_checksum $TMPDIR/area0
+	chks0=$(calc_sha256_checksum_file $TMPDIR/area0)
+	write_checksum $chks0 $TMPDIR/area0
+	write_luks2_hdr0 $TMPDIR/area0 $TGT_IMG
+	kill_bin_hdr $TMPDIR/hdr1
+	write_luks2_hdr1 $TMPDIR/hdr1 $TGT_IMG
+}
+
+function check()
+{
+	read_luks2_bin_hdr1 $TGT_IMG $TMPDIR/hdr_res1
+	local str_res1=$(head -c 6 $TMPDIR/hdr_res1)
+	test "$str_res1" = "VACUUM" || exit 2
+
+	read_luks2_json0 $TGT_IMG $TMPDIR/json_res0
+	jq -c 'if .segments | length < 2
+	       then error("Unexpected segments count") else empty end' $TMPDIR/json_res0 || exit 5
+}
+
+function cleanup()
+{
+	rm -f $TMPDIR/*
+	rm -fd $TMPDIR
+}
+
+test $# -eq 2 || exit 1
+
+TGT_IMG=$1/$(test_img_name $0)
+SRC_IMG=$2
+
+prepare
+generate
+check
+cleanup
diff --git a/tests/generators/generate-luks2-segment-wrong-backup-key-1.img.sh b/tests/generators/generate-luks2-segment-wrong-backup-key-1.img.sh
new file mode 100755
index 0000000..702fe71
--- /dev/null
+++ b/tests/generators/generate-luks2-segment-wrong-backup-key-1.img.sh
@@ -0,0 +1,67 @@
+#!/bin/bash
+
+. lib.sh
+
+#
+# *** Description ***
+#
+# generate primary header with wrong backup segment id
+#
+# secondary header is corrupted on purpose as well
+#
+
+# $1 full target dir
+# $2 full source luks2 image
+
+function prepare()
+{
+	cp $SRC_IMG $TGT_IMG
+	test -d $TMPDIR || mkdir $TMPDIR
+	read_luks2_json0 $TGT_IMG $TMPDIR/json0
+	read_luks2_bin_hdr0 $TGT_IMG $TMPDIR/hdr0
+	read_luks2_bin_hdr1 $TGT_IMG $TMPDIR/hdr1
+}
+
+function generate()
+{
+	# create illegal backup segment key (used to be bug in 32bit implementations)
+	json_str=$(jq -c '(.segments."0".offset | tonumber) as $i | .segments[range(1;65) | tostring] = { "type" : "linear", "offset" : ($i + 512 | tostring), "size" : "512" } | .segments."268435472" = { "type":"linear","offset":"512","size":"512","flags":["backup-x"]}' $TMPDIR/json0)
+	test ${#json_str} -lt $((LUKS2_JSON_SIZE*512)) || exit 2
+
+	write_luks2_json "$json_str" $TMPDIR/json0
+
+	merge_bin_hdr_with_json $TMPDIR/hdr0 $TMPDIR/json0 $TMPDIR/area0
+	erase_checksum $TMPDIR/area0
+	chks0=$(calc_sha256_checksum_file $TMPDIR/area0)
+	write_checksum $chks0 $TMPDIR/area0
+	write_luks2_hdr0 $TMPDIR/area0 $TGT_IMG
+	kill_bin_hdr $TMPDIR/hdr1
+	write_luks2_hdr1 $TMPDIR/hdr1 $TGT_IMG
+}
+
+function check()
+{
+	read_luks2_bin_hdr1 $TGT_IMG $TMPDIR/hdr_res1
+	local str_res1=$(head -c 6 $TMPDIR/hdr_res1)
+	test "$str_res1" = "VACUUM" || exit 2
+
+	read_luks2_json0 $TGT_IMG $TMPDIR/json_res0
+	jq -c 'if .segments | length < 64
+	       then error("Unexpected segments count") else empty end' $TMPDIR/json_res0 || exit 5
+}
+
+function cleanup()
+{
+	rm -f $TMPDIR/*
+	rm -fd $TMPDIR
+}
+
+test $# -eq 2 || exit 1
+
+TGT_IMG=$1/$(test_img_name $0)
+SRC_IMG=$2
+
+prepare
+generate
+check
+cleanup
diff --git a/tests/luks2-validation-test b/tests/luks2-validation-test
index 52945ba..04183fb 100755
--- a/tests/luks2-validation-test
+++ b/tests/luks2-validation-test
@@ -199,6 +199,8 @@ RUN luks2-segment-unknown-type.img			"R" "Validation rejected segment with all m
 RUN luks2-segment-two.img				"R" "Validation rejected two valid segments"
 RUN luks2-segment-wrong-flags.img			"F" "Failed to detect invalid flags field"
 RUN luks2-segment-wrong-flags-element.img		"F" "Failed to detect invalid flags content"
+RUN luks2-segment-wrong-backup-key-0.img		"F" "Failed to detect gap in backup segments"
+RUN luks2-segment-wrong-backup-key-1.img		"F" "Failed to detect gap in backup segments"
 
 echo "[6] Test metadata size and keyslots size (config section)"
 RUN luks2-invalid-keyslots-size-c0.img			"F" "Failed to detect too large keyslots_size in config section"