diff --git a/include/zephyr/net/buf.h b/include/zephyr/net/buf.h
index 9b1d5af16b3..88152bc9905 100644
--- a/include/zephyr/net/buf.h
+++ b/include/zephyr/net/buf.h
@@ -1049,7 +1049,7 @@ struct net_buf {
 		/** @endcond */
 	};
 
-	/** System metadata for this buffer. */
+	/** System metadata for this buffer. Cleared on allocation. */
 	uint8_t user_data[] __net_buf_align;
 };
 
diff --git a/subsys/net/buf.c b/subsys/net/buf.c
index 8267943dc01..6f0ee42f5c2 100644
--- a/subsys/net/buf.c
+++ b/subsys/net/buf.c
@@ -338,6 +338,7 @@ success:
 	buf->flags = 0U;
 	buf->frags = NULL;
 	buf->size  = size;
+	memset(buf->user_data, 0, buf->user_data_size);
 	net_buf_reset(buf);
 
 #if defined(CONFIG_NET_BUF_POOL_USAGE)