CVE Catalog

CVE-2026-81755

Low risk· EPSS 13%
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.23%

13th percentile - higher than 13% of all known CVEs

Summary

A vulnerability in the streaming RPC component of Apache bRPC (versions < 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. The server creates one response stream per stream identifier in the extra_stream_ids field without limiting the number of streams accepted in a single RPC, and each stream allocates its own bthread execution queue and resources.

Risk Assessment

An attacker can exhaust the memory of a bRPC server serving streaming RPC with a single request and make the service unavailable to all clients. The risk affects any bRPC deployment that accepts streams from untrusted clients.

Recommendation

Upgrade Apache bRPC to version 1.18.0 or apply the patch from PR #3493. After upgrading, review the new stream_max_streams_per_request gflag (default 64) and raise it only for applications that legitimately need more than 64 streams per RPC.

Other vulnerabilities in Apache bRPC

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Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS