diff --git a/ChangeLog.d/x509-programs-ip-san.txt b/ChangeLog.d/x509-programs-ip-san.txt
index a2e40ef032..6343777718 100644
--- a/ChangeLog.d/x509-programs-ip-san.txt
+++ b/ChangeLog.d/x509-programs-ip-san.txt
@@ -2,3 +2,5 @@ Bugfix
    * Fix a stack buffer overflow in the cert_write and cert_req sample
      programs when an IPv6 address is given in the san parameter. IPv6
      addresses are now written correctly.
+   * Fix the cert_write and cert_req sample programs writing the last IP
+     address for every IP entry when the san parameter has more than one.
diff --git a/programs/x509/cert_req.c b/programs/x509/cert_req.c
index 7deb706653..145c3e274b 100644
--- a/programs/x509/cert_req.c
+++ b/programs/x509/cert_req.c
@@ -152,9 +152,6 @@ int main(int argc, char *argv[])
     char *p, *q, *r;
     mbedtls_x509write_csr req;
     mbedtls_x509_san_list *cur, *prev;
-#if defined(MBEDTLS_X509_CRT_PARSE_C)
-    uint8_t ip[16] = { 0 };
-#endif
     /*
      * Set to sane values
      */
@@ -260,14 +257,23 @@ usage:
                     cur->node.type = MBEDTLS_X509_SAN_DNS_NAME;
                 } else if (strcmp(q, "IP") == 0) {
                     size_t ip_addr_len = 0;
+                    /* Each entry needs its own buffer, because the list is
+                     * only written once all entries have been parsed.
+                     * mbedtls_x509_crt_parse_cn_inet_pton() needs 16 bytes. */
+                    unsigned char *ip = mbedtls_calloc(1, 16);
+                    if (ip == NULL) {
+                        mbedtls_printf("Not enough memory for subjectAltName list\n");
+                        goto exit;
+                    }
                     cur->node.type = MBEDTLS_X509_SAN_IP_ADDRESS;
                     ip_addr_len = mbedtls_x509_crt_parse_cn_inet_pton(subtype_value, ip);
                     if (ip_addr_len == 0) {
                         mbedtls_printf("mbedtls_x509_crt_parse_cn_inet_pton failed to parse %s\n",
                                        subtype_value);
+                        mbedtls_free(ip);
                         goto exit;
                     }
-                    cur->node.san.unstructured_name.p = (unsigned char *) ip;
+                    cur->node.san.unstructured_name.p = ip;
                     cur->node.san.unstructured_name.len = ip_addr_len;
                 } else if (strcmp(q, "DN") == 0) {
                     cur->node.type = MBEDTLS_X509_SAN_DIRECTORY_NAME;
@@ -565,6 +571,9 @@ exit:
             mbedtls_free(dn->val.p);
             mbedtls_asn1_free_named_data_list(&dn->next);
         }
+        if (cur->node.type == MBEDTLS_X509_SAN_IP_ADDRESS) {
+            mbedtls_free(cur->node.san.unstructured_name.p);
+        }
         mbedtls_free(cur);
         cur = next;
     }
diff --git a/programs/x509/cert_write.c b/programs/x509/cert_write.c
index 95dc7d902d..40d70f5633 100644
--- a/programs/x509/cert_write.c
+++ b/programs/x509/cert_write.c
@@ -316,7 +316,6 @@ int main(int argc, char *argv[])
     size_t serial_len;
     mbedtls_asn1_sequence *ext_key_usage;
     mbedtls_x509_san_list *cur, *prev;
-    uint8_t ip[16] = { 0 };
     /*
      * Set to sane values
      */
@@ -642,14 +641,23 @@ usage:
                     cur->node.type = MBEDTLS_X509_SAN_DNS_NAME;
                 } else if (strcmp(q, "IP") == 0) {
                     size_t ip_addr_len = 0;
+                    /* Each entry needs its own buffer, because the list is
+                     * only written once all entries have been parsed.
+                     * mbedtls_x509_crt_parse_cn_inet_pton() needs 16 bytes. */
+                    unsigned char *ip = mbedtls_calloc(1, 16);
+                    if (ip == NULL) {
+                        mbedtls_printf("Not enough memory for subjectAltName list\n");
+                        goto exit;
+                    }
                     cur->node.type = MBEDTLS_X509_SAN_IP_ADDRESS;
                     ip_addr_len = mbedtls_x509_crt_parse_cn_inet_pton(subtype_value, ip);
                     if (ip_addr_len == 0) {
                         mbedtls_printf("mbedtls_x509_crt_parse_cn_inet_pton failed to parse %s\n",
                                        subtype_value);
+                        mbedtls_free(ip);
                         goto exit;
                     }
-                    cur->node.san.unstructured_name.p = (unsigned char *) ip;
+                    cur->node.san.unstructured_name.p = ip;
                     cur->node.san.unstructured_name.len = ip_addr_len;
                 } else if (strcmp(q, "DN") == 0) {
                     cur->node.type = MBEDTLS_X509_SAN_DIRECTORY_NAME;
@@ -1065,6 +1073,9 @@ exit:
             mbedtls_free(dn->val.p);
             mbedtls_asn1_free_named_data_list(&dn->next);
         }
+        if (cur->node.type == MBEDTLS_X509_SAN_IP_ADDRESS) {
+            mbedtls_free(cur->node.san.unstructured_name.p);
+        }
         mbedtls_free(cur);
         cur = next;
     }