diff --git a/libavformat/rmdec.c b/libavformat/rmdec.c
index 2edbfc37809a433f726088dff89264ac721db2b0..06a327e1c19962f2e431c4a3a3595124e2fe18ae 100644
--- a/libavformat/rmdec.c
+++ b/libavformat/rmdec.c
@@ -309,6 +309,9 @@ ff_rm_read_mdpr_codecdata (AVFormatContext *s, AVIOContext *pb,
     int64_t codec_pos;
     int ret;
 
+    if (codec_data_size < 0)
+        return AVERROR_INVALIDDATA;
+
     avpriv_set_pts_info(st, 64, 1, 1000);
     codec_pos = avio_tell(pb);
     v = avio_rb32(pb);