diff --git a/libavformat/oggparsevorbis.c b/libavformat/oggparsevorbis.c
index 7c97807c01..82029daf93 100644
--- a/libavformat/oggparsevorbis.c
+++ b/libavformat/oggparsevorbis.c
@@ -35,27 +35,28 @@ vorbis_comment(AVFormatContext * as, uint8_t *buf, int size)
 {
     const uint8_t *p = buf;
     const uint8_t *end = buf + size;
-    unsigned s, n, j;
+    unsigned n, j;
+    int s;
 
     if (size < 8) /* must have vendor_length and user_comment_list_length */
         return -1;
 
     s = bytestream_get_le32(&p);
 
-    if (end - p < s)
+    if (end - p - 4 < s || s < 0)
         return -1;
 
     p += s;
 
     n = bytestream_get_le32(&p);
 
-    while (p < end && n > 0) {
+    while (end - p >= 4 && n > 0) {
         const char *t, *v;
         int tl, vl;
 
         s = bytestream_get_le32(&p);
 
-        if (end - p < s)
+        if (end - p < s || s < 0)
             break;
 
         t = p;