---
id: "CVE-2026-80463"
kind: "vulnerability"
aliases: ["CVE-2026-80463"]
title: "Apache bRPC: unbounded stream reassembly lets remote peers exhaust server memory"
severity: "unknown"
cvss: null
epss: 0.00202
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["apache-brpc", "bpc", "c++", "package", "self-hosted", "streaming-rpc"]
not_affected_if: ["no-streams-from-untrusted-clients", "version-1.18.0-or-later"]
published_at: "2026-10-21T12:17:24+00:00"
first_seen_at: "2026-10-23T21:57:28+00:00"
updated_at: "2026-10-25T05:02:35+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-80463", "first_seen_at": "2026-10-23T21:57:28+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-80463", "first_seen_at": "2026-10-24T13:15:54+00:00"}]
---

# Apache bRPC: unbounded stream reassembly lets remote peers exhaust server memory

Apache bRPC before 1.18.0 buffers continuation frames of a fragmented stream message without any size limit. A remote peer that can open a stream can send an endless sequence of these frames and drive the server out of memory, crashing it.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the bRPC version in use, for example with `grep -r BRPC_VERSION` in the build tree or the package manager's version of the bRPC library; affected if below `1.18.0`.
- Look for services that call `brpc::StreamAccept` or `brpc::StreamCreate` over the built-in streaming protocol and accept connections from untrusted clients.

## Fix

- Upgrade bRPC to `1.18.0` or later.
- Alternatively, apply the patch from https://github.com/apache/brpc/pull/3489.
- Note that after the fix, fragmented stream messages larger than `max_body_size` (default 64MB) are rejected with EMSGSIZE; raise the gflag `max_body_size` if legitimate messages are larger.

## Timeline

- 2026-10-23T21:57:28+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-80463
- 2026-10-24T13:15:54+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-80463

## From the sources

Unbounded memory accumulation in the stream message reassembly path of Apache bRPC (version < 1.18.0) on all platforms allows remote attackers to exhaust the memory of a server (denial of service) by sending an endless sequence of continuation data frames.

Root Cause:
The streaming RPC protocol bounds every single data frame by max_body_size, but a fragmented stream message accumulates continuation frames into one buffer (_pending_buf) without any limit on the accumulated size. A malicious peer that can open a stream can therefore keep sending continuation frames to make the receiver accumulate an arbitrarily large in-memory message. Since the default flow-control settings (socket_max_streams_unconsumed_bytes=0) do not throttle the sending rate, the receiver's memory grows until the process runs out of memory and crashes or becomes unavailable.

Affected Scenarios:
Services that accept streams from untrusted clients (for example using brpc::StreamAccept or brpc::StreamCreate with the built-in streaming protocol) are affected.


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/3489 


Note:
The fix limits the accumulated payload of a fragmented stream message to max_body_size (default 64MB). When the accumulated payload exceeds the limit, the pending fragments are released and the stream is closed with error EMSGSIZE. After applying the fix, legitimate fragmented stream messages larger than max_body_size will be rejected; you can adjust the gflag max_body_size to change the limit.

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