CVE-2026-81755: Apache bRPC: Uncontrolled Resource Consumption via Excessive Streams in a Single RPC Request

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of 29 Oct 2026. If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?

0.2%

EPSS score, percentile 14.2 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

Not scored

The CVE record carries no CVSS score.

What should I do?

CISA has set no required action, because the vulnerability is not in KEV.

Advisories and patches (1)

Which versions are affected?

Affected

• before 1.18.0

Versions by product

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026; CVE List, as of 29 Oct 2026. About the data.

What to do

Advisories and patches

• lists.apache.org (Vendor advisory)

This summary is based on the CVE record as of 29 Oct 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

As listed in the CVE record.

Versions not listed are: unaffected.

Source: CVE List, as of 29 Oct 2026. About the data.

About this vulnerability

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…

Summary: CVE record, as of 29 Oct 2026.

• CISA has not added CVE-2026-81755 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
• The CVE record was published on 21 Oct 2026.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.2% (percentile 14.2), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
• The credits in the CVE record name Anthropic (Claude) as finder.

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; CVE List, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026. About the data.

Description

Apache bRPC: Uncontrolled Resource Consumption via Excessive Streams in a Single RPC Request

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.

Source: CVE List, as of 29 Oct 2026. About the data.

Timeline

Known exploited Apache vulnerabilities

• CVE-2016-3081: Apache Struts Command Injection Vulnerability (added 8 Oct 2026)
• CVE-2026-34486: Apache Tomcat Missing Encryption of Sensitive Data Vulnerability (added 4 Aug 2026)
• CVE-2026-34197: Apache ActiveMQ Improper Input Validation Vulnerability (added 16 Apr 2026)
• CVE-2024-38475: Apache HTTP Server Improper Escaping of Output Vulnerability (added 1 May 2025)
• CVE-2025-24813: Apache Tomcat Path Equivalence Vulnerability (added 1 Apr 2025)