CVE-2026-81755

Deferred Deferred - Pending Action

BaseFortify

Publication date: 2026-10-21

Last updated on: 2026-10-30

Assigner: Apache Software Foundation

Description

Uncontrolled resource consumption in the streaming RPC component of Apache bRPC (version < 1.18.0) allows a remote attacker to exhaust server memory and cause denial of service by sending a single RPC request that declares an excessive number of streams. Root Cause: In the streaming RPC feature, a client can declare multiple streams in one RPC request by putting extra stream identifiers into the repeated field `stream_settings.extra_stream_ids` of the RPC meta. On the server side, `StreamAccept` creates one response stream for every stream identifier declared by the request, without limiting the number of streams accepted in a single RPC. The request body size is only bounded by `max_body_size` (default 64MB), which is enough to carry millions of stream identifiers. Each accepted stream allocates its own bthread execution queue and associated resources, so a single crafted request can make the server create a huge number of streams and exhaust memory, leading to denial of service. Affected Scenarios: Use a bRPC server that serves streaming RPC and calls `StreamAccept` to accept streams from untrusted clients. How to Fix: (Choose one of the following options) 1. Upgrade bRPC to the 1.18.0 version. 2. Apply this patch: https://github.com/apache/brpc/pull/3493 Note: The fix adds a new gflag `stream_max_streams_per_request` with a default value of 64. Requests declaring more streams than the limit are rejected before any response stream is created. Applications that legitimately need to accept more than 64 streams in one RPC must raise this flag; otherwise such requests will fail after applying the fix.

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Meta Information

Published

2026-10-21

Last Modified

2026-10-30

Generated

2026-11-10

AI Q&A

2026-10-21

EPSS Evaluated

2026-11-09

NVD

CVE-2026-81755

EUVD

EUVD-2026-107189

Affected Vendors & Products

Vendor	Product	Version / Range
Apache Software Foundation	Apache bRPC	0

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-400	The product does not properly control the allocation and maintenance of a limited resource.

Attack-Flow Graph

Executive Summary

This vulnerability is an uncontrolled resource consumption issue in Apache bRPC versions before 1.18.0. It allows a remote attacker to send a single RPC request with an excessive number of stream identifiers, causing the server to create millions of response streams. Each stream consumes memory and system resources, leading to a denial of service.

Detection Guidance

Detecting this vulnerability requires monitoring for unusual memory consumption or RPC request patterns. Check server logs for requests with excessive stream identifiers in the `stream_settings.extra_stream_ids` field. Use system monitoring tools like `top`, `htop`, or `ps` to observe abnormal memory usage by the bRPC server process.

Impact Analysis

If you run a bRPC server that handles streaming RPC requests from untrusted clients, this vulnerability could allow attackers to crash your server by exhausting its memory. This results in service disruption and potential downtime for your applications.

Compliance Impact

This vulnerability could impact compliance with GDPR and HIPAA by enabling denial-of-service attacks that disrupt service availability. GDPR requires maintaining system availability, while HIPAA mandates safeguards against service disruptions. Exploiting this flaw may lead to violations of these requirements.

Mitigation Strategies

Immediately upgrade bRPC to version 1.18.0 or apply the patch from https://github.com/apache/brpc/pull/3493. If upgrading is not possible, restrict untrusted client access to the streaming RPC service until the fix is applied.

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