CVE-2026-74758: Apache bRPC: Heap Use-After-Free in RTMP Abort Message Handling

A heap use-after-free in the RTMP protocol component of Apache bRPC (versions < 1.18.0) allows a remote attacker to crash a bRPC RTMP server by sending a crafted Abort control message. No authentication or application-level request is required.

Root Cause: When an RTMP Abort control message names the chunk stream that is currently being parsed (the chunk stream carrying the message itself), RtmpChunkStream::OnAbortMessage calls RtmpContext::ClearChunkStream, which deletes the RtmpChunkStream while its Feed() is still running. After the message handler returns, Feed() continues to access members of the deleted object, resulting in a heap-use-after-free.

Affected Scenarios: bRPC servers that enable RTMP support (ServerOptions.rtmpservice set) and accept connections from untrusted networks.

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/3452

The fix skips clearing the chunk stream when the Abort message targets the chunk stream that is currently being parsed.