diff --git a/sys/base64/base64.c b/sys/base64/base64.c
index 869ca668ad..849ba8ca21 100644
--- a/sys/base64/base64.c
+++ b/sys/base64/base64.c
@@ -108,10 +108,6 @@ int base64_encode(unsigned char *data_in, size_t data_in_size, \
     /* The last character is not finished yet */
     njump++;
 
-    if (njump == 4) {
-        nNum = (tmpval >> (2 * njump));
-    }
-
     nNum = nLst << (8 - 2 * njump);
     base64_out[iterate_base64_buffer++] = getsymbol(nNum);
 
diff --git a/sys/bloom/bloom.c b/sys/bloom/bloom.c
index 3ad77ffa90..b393aa02f9 100644
--- a/sys/bloom/bloom.c
+++ b/sys/bloom/bloom.c
@@ -35,7 +35,7 @@ bloom_t *bloom_new(size_t size, size_t num_hashes, ...)
     }
 
     /* Allocate Bloom array */
-    if (!(bloom->a = calloc(ROUND(size), sizeof(char)))) {
+    if (!(bloom->a = calloc(ROUND(size), sizeof(uint8_t)))) {
         free(bloom);
         return NULL;
     }
diff --git a/sys/crypto/modes/ccm.c b/sys/crypto/modes/ccm.c
index 8c0a909392..a9ccc9a408 100644
--- a/sys/crypto/modes/ccm.c
+++ b/sys/crypto/modes/ccm.c
@@ -40,7 +40,7 @@ int ccm_compute_cbc_mac(cipher_t* cipher, uint8_t iv[16],
     uint8_t offset, block_size, mac_enc[16] = {0};
 
     block_size = cipher_get_block_size(cipher);
-    memcpy(mac, iv, 16);
+    memmove(mac, iv, 16);
     offset = 0;
     do {
         uint8_t block_size_input = (length - offset > block_size) ?
diff --git a/sys/embunit/stdImpl.c b/sys/embunit/stdImpl.c
index 5068be8a36..8a45259be1 100644
--- a/sys/embunit/stdImpl.c
+++ b/sys/embunit/stdImpl.c
@@ -103,17 +103,18 @@ int stdimpl_strcmp(const char *s1, const char *s2)
     if (s1 == s2) {
         return 0;
     }
-    else if (s1 && !s2) {
+    else if (s1 == NULL) {
+        return -1;
+    }
+    else if (s2 == NULL) {
         return +1;
     }
-    else if (!s1 && s2) {
-        return -1;
-    } else {
-        char c1,c2;
+    else {
+        char c1, c2;
         do {
             c1 = *s1++;
             c2 = *s2++;
-        } while (c1 && c2 && (c1==c2));
+        } while ((c1 == c2) && (c1 != '\0'));
         return c1 - c2;
     }
 }
diff --git a/sys/ubjson/ubjson-read.c b/sys/ubjson/ubjson-read.c
index d2886526a4..f3de9a3eec 100644
--- a/sys/ubjson/ubjson-read.c
+++ b/sys/ubjson/ubjson-read.c
@@ -104,6 +104,8 @@ ssize_t ubjson_get_i32(ubjson_cookie_t *restrict cookie, ssize_t content, int32_
             case UBJSON_INT32_INT32:
                 *dest = (int32_t) byteorder_ntohl(value.i32);
                 break;
+            default:
+                return -1;
         }
     }
     return result;
@@ -134,7 +136,9 @@ static ubjson_read_callback_result_t _ubjson_read_length(ubjson_cookie_t *restri
     if (type == UBJSON_TYPE_INT32) {
         int32_t len32;
         read = ubjson_get_i32(cookie, content, &len32);
-        len64 = len32;
+        if (read > 0) {
+            len64 = len32;
+        }
     }
     else if (type == UBJSON_TYPE_INT64) {
         read = ubjson_get_i64(cookie, content, &len64);
diff --git a/tests/unittests/tests-cbor/tests-cbor.c b/tests/unittests/tests-cbor/tests-cbor.c
index a66fa89c75..557bd53cf1 100644
--- a/tests/unittests/tests-cbor/tests-cbor.c
+++ b/tests/unittests/tests-cbor/tests-cbor.c
@@ -351,6 +351,7 @@ static void test_array(void)
         TEST_ASSERT_EQUAL_INT(1, i);
         offset += cbor_deserialize_int(&stream, offset, &i);
         TEST_ASSERT_EQUAL_INT(2, i);
+        TEST_ASSERT_EQUAL_INT(sizeof(data), offset);
     }
 
     cbor_clear(&stream);
@@ -374,6 +375,7 @@ static void test_array(void)
         char buffer[1024];
         offset += cbor_deserialize_byte_string(&stream, offset, buffer, sizeof(buffer));
         TEST_ASSERT_EQUAL_STRING("a", &(buffer[0]));
+        TEST_ASSERT_EQUAL_INT(sizeof(data), offset);
     }
 }
 
@@ -442,6 +444,7 @@ static void test_map(void)
         TEST_ASSERT_EQUAL_INT(2, key);
         offset += cbor_deserialize_byte_string(&stream, offset, value, sizeof(value));
         TEST_ASSERT_EQUAL_STRING("2", &(value[0]));
+        TEST_ASSERT_EQUAL_INT(sizeof(data), offset);
     }
 }