# CVE-2026-84727: Apache bRPC: Use-After-Free in RTMP Chunk Stream Handling via Abort Message


- **Severity:** Medium 5.4 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 21 Oct 2026
- **Updated:** 21 Oct 2026
- **Also known as:** GHSA-qqp7-xh38-h7v3

## What is CVE-2026-84727?

CVE-2026-84727 is a medium-severity vulnerability in Apache bRPC, published on 21 Oct 2026. 

### Official description

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

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-84727?


## How do I fix CVE-2026-84727?

No fix has been published for CVE-2026-84727 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-84727 being exploited?

There is no known exploitation of CVE-2026-84727 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-84727 and fix it if it is affected.

What it is: CVE-2026-84727 is a medium-severity vulnerability in Apache bRPC, published on 21 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-84727 in the wild and no public exploit code.

Affected product: Apache bRPC. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-84727/ (Markdown: https://insights.sbomify.com/CVE-2026-84727/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-84727
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-84727
- OSV: https://osv.dev/vulnerability/CVE-2026-84727

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-84727/
Summaries are generated and may contain mistakes; the official description above is the record.