diff --git a/libavcodec/ptx.c b/libavcodec/ptx.c
index 42147f4afc..19f9305cda 100644
--- a/libavcodec/ptx.c
+++ b/libavcodec/ptx.c
@@ -55,6 +55,9 @@ static int ptx_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
 
     buf += offset;
 
+    if (buf_end - buf < w * bytes_per_pixel)
+        return AVERROR_INVALIDDATA;
+
     if ((ret = ff_set_dimensions(avctx, w, h)) < 0)
         return ret;