diff --git a/chromecast/media/cma/backend/mixer/mixer_input_connection.cc b/chromecast/media/cma/backend/mixer/mixer_input_connection.cc
index f7bb2acd2aa17..d16a16d5465a3 100644
--- a/chromecast/media/cma/backend/mixer/mixer_input_connection.cc
+++ b/chromecast/media/cma/backend/mixer/mixer_input_connection.cc
@@ -638,7 +638,13 @@ void MixerInputConnection::RestartPlaybackAt(int64_t timestamp, int64_t pts) {
 void MixerInputConnection::SetMediaPlaybackRate(double rate) {
   DCHECK(io_task_runner_->RunsTasksInCurrentSequence());
   LOG(INFO) << this << " SetMediaPlaybackRate rate=" << rate;
-  DCHECK_GT(rate, 0);
+  // |rate| comes off an unauthenticated local socket. A non-positive rate
+  // produces a negative |frames_to_crop| in FillTimestampedAudio() and a heap
+  // OOB read in FillFromQueue(). Reject it instead of DCHECKing.
+  if (!(rate > 0)) {
+    LOG(WARNING) << this << " Rejecting invalid playback rate " << rate;
+    return;
+  }
 
   base::AutoLock lock(lock_);
   if (state_ == State::kGotEos || state_ == State::kRemoved) {