CVE-2026-84727: Apache bRPC: Use-After-Free in RTMP Chunk Stream Handling via Abort Message
Use-after-free in the RTMP protocol implementation in Apache bRPC (version < 1.18.0) on all platforms allows a malicious RTMP peer to crash the process or potentially corrupt memory via a crafted Abort message.
Root Cause: When processing an RTMP Abort (protocol control message type 2), the RTMP policy implementation deleted the target RtmpChunkStream object. The send path (RtmpUnsentMessage::AppendAndDestroySelf -> RtmpChunkStream::SerializeMessage) runs concurrently on sender threads and dereferences the same RtmpChunkStream object without synchronization. If a remote peer sends an Abort message naming a chunk stream that is concurrently being used to serialize an outgoing message, the stream object is freed while still in use, resulting in a use-after-free. Additionally, deleting the chunk stream discarded its previous message header, so subsequent compressed (type-3) chunk headers on that stream could no longer be decoded.
Affected Scenarios: Any application using the bRPC RTMP protocol implementation (rtmp policy), either as an RTMP server or as an RTMP client, where the remote endpoint is untrusted. The attacker needs to send an Abort message targeting a chunk stream id that is concurrently used for sending, which can crash the process or lead to memory corruption.
How to Fix: (Choose one of the following options) 1. Upgrade bRPC to version 1.18.0, which fixes this issue. 2. Apply this patch: https://github.com/apache/brpc/pull/3515
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Apache bRPCto a version that resolves this vulnerability.Fixed in 1.18.0
Event History
Frequently Asked Questions
Which deployments are exposed?
Applications using the Apache bRPC RTMP protocol implementation (rtmp policy) are affected when they operate as either an RTMP server or client and communicate with an untrusted remote endpoint. The issue affects versions earlier than 1.18.0 on all platforms.
What does an attacker need to do to trigger the issue?
The attacker must be an RTMP peer able to send a crafted Abort message that names a chunk stream ID being used concurrently to serialize an outgoing message. This race can cause a process crash or potentially corrupt memory.
How can I determine whether my application is affected?
Check whether the application uses bRPC's rtmp policy and runs a version earlier than 1.18.0. If an untrusted RTMP peer can connect to it, or it can connect to an untrusted RTMP endpoint, it is in an affected scenario.