diff --git a/src/core/thread/mesh_forwarder.cpp b/src/core/thread/mesh_forwarder.cpp
index 6398181bf..ff9cf0094 100644
--- a/src/core/thread/mesh_forwarder.cpp
+++ b/src/core/thread/mesh_forwarder.cpp
@@ -1583,6 +1583,7 @@ otError MeshForwarder::GetFramePriority(uint8_t *           aFrame,
     }
     else
     {
+        VerifyOrExit(aFrameLength >= sizeof(Ip6::UdpHeader), error = OT_ERROR_PARSE);
         memcpy(&udpHeader, aFrame, sizeof(Ip6::UdpHeader));
     }