diff --git a/sys/clif/clif.c b/sys/clif/clif.c
index 7376a196d9..b52b7565dc 100644
--- a/sys/clif/clif.c
+++ b/sys/clif/clif.c
@@ -251,12 +251,14 @@ ssize_t clif_get_attr(const char *input, size_t input_len, clif_attr_t *attr)
     assert(attr);
     const char *pos = input;
     const char *end = input + input_len;
-    bool quoted = false;
+    unsigned quotes = 0;
     bool scan_value = false;
 
     /* initialize attr */
     attr->value = NULL;
     attr->key = NULL;
+    attr->key_len = 0;
+    attr->value_len = 0;
 
     if (input_len == 0) {
         return CLIF_NOT_FOUND;
@@ -283,10 +285,11 @@ ssize_t clif_get_attr(const char *input, size_t input_len, clif_attr_t *attr)
             /* check if the value is quoted and prepare pointer for value scan */
             pos++;
             if (pos == end) {
-                break;
+                /* found attribute-value separator but no value */
+                return CLIF_NOT_FOUND;
             }
             else if (*pos == '"') {
-                quoted = true;
+                quotes++;
                 pos++;
             }
             attr->value = (char *)pos;
@@ -299,15 +302,23 @@ ssize_t clif_get_attr(const char *input, size_t input_len, clif_attr_t *attr)
     if (scan_value) {
         /* iterate over value */
         while (pos < end) {
-            if (quoted) {
+            if (quotes == 1) {
+                /* we can safely access *(pos - 1) because at least one
+                 * character was detected to get to this point */
                 if (*pos == '"' && *(pos - 1) != '\\') {
                     /* found unescaped quote */
                     attr->value_len = pos - attr->value;
+                    quotes++;
                     pos++;
                     break;
                 }
             }
             else {
+                if (*pos == '"') {
+                    /* not valid */
+                    return CLIF_NOT_FOUND;
+                }
+
                 if (*pos == LF_ATTR_SEPARATOR_C || *pos == LF_LINK_SEPARATOR_C) {
                     /* value ends */
                     attr->value_len = pos - attr->value;
@@ -316,6 +327,11 @@ ssize_t clif_get_attr(const char *input, size_t input_len, clif_attr_t *attr)
             }
             pos++;
         }
+
+        if (!attr->value_len) {
+            DEBUG("Empty value found");
+            return CLIF_NOT_FOUND;
+        }
     }
     else {
         /* buffer exhausted and no special character found, calculate length of
@@ -323,6 +339,12 @@ ssize_t clif_get_attr(const char *input, size_t input_len, clif_attr_t *attr)
         attr->key_len = pos - attr->key;
     }
 
+    /* either the value is unquoted (0) or quoted (2) */
+    if (quotes % 2U) {
+        DEBUG("Incorrect number of unescaped quotes found: %d\n", quotes);
+        return CLIF_NOT_FOUND;
+    }
+
     return pos - input;
 }