--- a/libtomcrypt/src/pk/asn1/der/sequence/der_decode_sequence_flexi.c	Wed Jun 10 23:01:33 2020 +0800
+++ b/libtomcrypt/src/pk/asn1/der/sequence/der_decode_sequence_flexi.c	Wed Jun 10 23:16:13 2020 +0800
@@ -79,8 +79,8 @@
 */
 int der_decode_sequence_flexi(const unsigned char *in, unsigned long *inlen, ltc_asn1_list **out)
 {
-   ltc_asn1_list *l;
-   unsigned long err, type, len, totlen, data_offset;
+   ltc_asn1_list *l, *t;
+   unsigned long err, type, len, totlen, data_offset, len_len;
    void          *realloc_tmp;
 
    LTC_ARGCHK(in    != NULL);
@@ -407,6 +407,17 @@
                 l->child->parent = l;
              }
 
+             t = l;
+             len_len = 0;
+             while((t != NULL) && (t->child != NULL)) {
+                len_len++;
+                t = t->child;
+             }
+             if (len_len > LTC_DER_MAX_RECURSION) {
+                err = CRYPT_ERROR;
+                goto error;
+             }
+
              break;
 
          case 0x80: /* Context-specific */