diff --git a/libavcodec/parser.c b/libavcodec/parser.c
index 670680ea7c..1b50f40b20 100644
--- a/libavcodec/parser.c
+++ b/libavcodec/parser.c
@@ -262,6 +262,9 @@ int ff_combine_frame(ParseContext *pc, int next,
     for (; pc->overread > 0; pc->overread--)
         pc->buffer[pc->index++] = pc->buffer[pc->overread_index++];
 
+    if (next > *buf_size)
+        return AVERROR(EINVAL);
+
     /* flush remaining if EOF */
     if (!*buf_size && next == END_NOT_FOUND)
         next = 0;