diff --git a/library/rsa.c b/library/rsa.c
index 191bfe8..637c23a 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -794,6 +794,9 @@
             hlen = md_get_size( md_info );
             slen = hlen;
 
+            if( olen < hlen + slen + 2 )
+                return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
+
             memset( sig, 0, olen );
             memset( &md_ctx, 0, sizeof( md_context_t ) );