diff --git a/libavcodec/zmbv.c b/libavcodec/zmbv.c
index c16d912117..82ae169ef4 100644
--- a/libavcodec/zmbv.c
+++ b/libavcodec/zmbv.c
@@ -410,11 +410,16 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPac
     int hi_ver, lo_ver, ret;
 
     /* parse header */
+    if (len < 1)
+        return AVERROR_INVALIDDATA;
     c->flags = buf[0];
     buf++; len--;
     if (c->flags & ZMBV_KEYFRAME) {
         void *decode_intra = NULL;
         c->decode_intra= NULL;
+
+        if (len < 6)
+            return AVERROR_INVALIDDATA;
         hi_ver = buf[0];
         lo_ver = buf[1];
         c->comp = buf[2];