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CVE-2026-81755

HIGHCVSS 7.5/10EPSS 0.23%

Last modified

CVE-2026-81755 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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. EPSS estimates a 0.23% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability
0.23%

14.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
Apache Software FoundationApache bRPC< 1.18.0

References

Timeline

Published
Last Modified
Status
Deferred

Frequently Asked Questions

What is CVE-2026-81755?
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.
How severe is CVE-2026-81755?
CVE-2026-81755 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.23% probability of exploitation in the next 30 days.
How do I fix CVE-2026-81755?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST