diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 0927b0b9c06b..d121c8f22028 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -3431,6 +3431,18 @@ int cs_etm__process_auxtrace_info_full(union perf_event *event,
 	/* First the global part */
 	ptr = (u64 *) auxtrace_info->priv;
 	num_cpu = ptr[CS_PMU_TYPE_CPUS] & 0xffffffff;
+
+	/*
+	 * Bound num_cpu by the event size: the global header consumes
+	 * CS_ETM_HEADER_SIZE bytes, and each CPU needs at least one u64
+	 * metadata entry after that.
+	 */
+	priv_size = total_size - event_header_size - INFO_HEADER_SIZE -
+		    CS_ETM_HEADER_SIZE;
+	if (num_cpu <= 0 || priv_size <= 0 ||
+	    num_cpu > priv_size / (int)sizeof(u64))
+		return -EINVAL;
+
 	metadata = zalloc(sizeof(*metadata) * num_cpu);
 	if (!metadata)
 		return -ENOMEM;