diff --git a/library/cipher.c b/library/cipher.c
index 0683677..f883171 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -849,6 +849,9 @@
     }
 
     padding_len = input[input_len - 1];
+    if (padding_len == 0 || padding_len > (int)input_len) {
+        return MBEDTLS_ERR_CIPHER_INVALID_PADDING;
+    }
     *data_len = input_len - padding_len;
 
     mbedtls_ct_condition_t bad = mbedtls_ct_uint_gt(padding_len, input_len);