From c7ecaf234fc3345faa149b64833e7701b54f4cbb Mon Sep 17 00:00:00 2001
From: Tim Perry <pimterry@gmail.com>
Date: Fri, 24 Jul 2026 14:48:01 +0200
Subject: [PATCH] quic: fix infinite loop if STOP_SENDING received on a
 buffering stream

Signed-off-by: Tim Perry <pimterry@gmail.com>
---
 src/quic/application.cc                       |  6 +++
 ...test-quic-stream-stop-sending-buffered.mjs | 49 +++++++++++++++++++
 2 files changed, 55 insertions(+)
 create mode 100644 test/parallel/test-quic-stream-stop-sending-buffered.mjs

diff --git a/src/quic/application.cc b/src/quic/application.cc
index 688a1309dea552..79a3263b8537a9 100644
--- a/src/quic/application.cc
+++ b/src/quic/application.cc
@@ -410,6 +410,12 @@ class DefaultApplication final : public Session::Application {
 
   void ResumeStream(stream_id id) override { ScheduleStream(id); }
 
+  void StreamWriteShut(stream_id id) override {
+    if (auto stream = session().FindStream(id)) [[likely]] {
+      stream->Unschedule();
+    }
+  }
+
   void BlockStream(stream_id id) override {
     if (auto stream = session().FindStream(id)) [[likely]] {
       // Remove the stream from the send queue. It will be re-scheduled
diff --git a/test/parallel/test-quic-stream-stop-sending-buffered.mjs b/test/parallel/test-quic-stream-stop-sending-buffered.mjs
new file mode 100644
index 00000000000000..1d41635b4575d3
--- /dev/null
+++ b/test/parallel/test-quic-stream-stop-sending-buffered.mjs
@@ -0,0 +1,49 @@
+// Flags: --experimental-quic --no-warnings
+
+// A peer STOP_SENDING must unschedule buffered outbound data.
+
+import { hasQuic, mustCall, skip } from '../common/index.mjs';
+import assert from 'node:assert';
+
+if (!hasQuic) {
+  skip('QUIC is not enabled');
+}
+
+const { connect, listen } = await import('../common/quic.mjs');
+
+const serverStreamReady = Promise.withResolvers();
+const clientBuffered = Promise.withResolvers();
+const serverReset = Promise.withResolvers();
+
+const serverEndpoint = await listen(mustCall((serverSession) => {
+  serverSession.onstream = mustCall(async (stream) => {
+    serverStreamReady.resolve();
+    await clientBuffered.promise;
+
+    const closed = assert.rejects(stream.closed, {
+      code: 'ERR_QUIC_APPLICATION_ERROR',
+    });
+    stream.stopSending(1n);
+    stream.writer.endSync();
+    await closed;
+    serverSession.close();
+    serverReset.resolve();
+  });
+}));
+
+const clientSession = await connect(serverEndpoint.address);
+await clientSession.opened;
+
+const stream = await clientSession.createBidirectionalStream();
+const clientClosed = stream.closed.catch(() => {});
+const writer = stream.writer;
+writer.writeSync(new Uint8Array([1]));
+await serverStreamReady.promise;
+
+writer.writeSync(new Uint8Array(64 * 1024));
+clientBuffered.resolve();
+
+await serverReset.promise;
+
+await Promise.all([clientClosed, clientSession.closed]);
+await serverEndpoint.close();