diff --git a/libavcodec/mmvideo.c b/libavcodec/mmvideo.c
index 4214eeb964..b74424cc13 100644
--- a/libavcodec/mmvideo.c
+++ b/libavcodec/mmvideo.c
@@ -104,6 +104,9 @@ static int mm_decode_intra(MmContext * s, int half_horiz, int half_vert)
         if (half_horiz)
             run_length *=2;
 
+        if (run_length > s->avctx->width - x)
+            return AVERROR_INVALIDDATA;
+
         if (color) {
             memset(s->frame.data[0] + y*s->frame.linesize[0] + x, color, run_length);
             if (half_vert)