CVE-2026-82210: Apache bRPC: Remote denial of service (crash) via malformed stream feedback frames

Enforceable assertion in the streaming feature of Apache bRPC (version < 1.18.0) on all platforms allows a remote attacker to crash the server process by sending a malformed stream feedback frame.

Root Cause: When handling FRAMETYPEFEEDBACK frames, bRPC calls Stream::SetRemoteConsumed() which contains CHECK(curbufsize > 0) and unconditionally asserts CHECK(buf.IsEmpty()) on the frame payload. A feedback frame that carries an unexpected payload, or a feedback frame received on a stream where flow control is disabled (curbufsize == 0), reaches these assertions. On failure, CHECK failures abort the process, allowing an unauthenticated single client (once a stream is established) to terminate the server and cause a denial of service.

Affected Scenarios: Use bRPC server with the streaming control feature (Stream API) served from untrusted network.

How to Fix: 1. Upgrade bRPC to version 1.18.0, which fixes this issue. 2. Apply this patch: https://github.com/apache/brpc/pull/3494

The fix rejects malformed feedback frames with EPROTO and closes only the affected stream instead of crashing the whole process, and it bounds buffer shrinking so curbufsize never drops to 0 while flow control is enabled.