capmt: add protection for out-of-valid-data access, fixes #4430

diff --git a/src/descrambler/capmt.c b/src/descrambler/capmt.c
index c3a84b4e4dbdc9e281dfcb469d639c78f60bf231..fc196e63dc3f3f7ee7e80434ce6422b93c0c4751 100644 (file)
--- a/src/descrambler/capmt.c
+++ b/src/descrambler/capmt.c
@@ -1644,6 +1644,8 @@ handle_single(capmt_t *capmt)
         offset = 0;
         cmd_size = 0;
         cmd = 0;
+        if (buffer.sb_ptr < 5)
+          break;
         if (netproto) {
           buffer.sb_bswap = 1;
           cmd_size = capmt_msg_size(capmt, &buffer, 0);