External risk intelligence

Apache bRPC Missing Authentication in Streaming RPC Path Leads to Unauthorized Frame Injection

CVE advisorySeverity: CRITICAL (CVSS 9.1)

CVE-2026-78334

Apache bRPC is a framework used to build high-performance RPC servers and services. These services are commonly deployed as network-accessible backends, APIs, or edge services that handle incoming streaming data. Because these services are designed for remote communication and the vulnerability affects the streaming RPC path, they are commonly reachable over network segments.

Missing Authentication

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A vulnerability in Apache bRPC's streaming functionality allows unauthorized remote access to server components, potentially enabling data injection or delivery. This could impact services that handle streaming data and are configured with authentication.

Bypasses authentication for streaming data.
Enables unauthorized data injection or delivery.
Confirms if bRPC streaming is used.

Attack Path

How an attacker could exploit the issue

A remote attacker can exploit this vulnerability by sending specially crafted streaming frames to a bRPC server that has authentication configured but is accessible from an untrusted network. This bypasses the authentication mechanism, allowing the attacker to inject or deliver unauthorized data through streaming RPCs. The vulnerability stems from how streaming frames are parsed and how streams are bound, enabling an unauthenticated peer to exchange frames or an external connection to impersonate a stream.

No authentication needed to start.
Bypasses authentication in streaming RPCs.
Unauthorized data injection or delivery.

Live Threat

Current exploitation, exposure, and threat context

When a bRPC server is configured with authentication and exposed to an untrusted network, it could allow remote attackers to bypass authentication and deliver unauthorized streaming frames. This could impact the integrity and availability of services relying on these streaming RPCs.

Server-side streaming RPC data
Unauthorized frames delivered remotely
Service integrity and availability

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in Apache bRPC's streaming RPC path, if authentication is configured, allows remote attackers to bypass server authentication. The initial action should focus on identifying all deployments of bRPC, determining their exposure to untrusted networks, and confirming if they are configured with authentication and serve streaming RPC. Following this, owners should be identified to plan remediation based on assessed risk.

Application and platform teams own this.
Verify bRPC servers serving streaming RPC.
Plan remediation based on risk.

Supplementary metadata

CVSS vector

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Frequently asked questions

What is Apache bRPC?

Apache bRPC is an industrial-grade framework designed to build high-performance Remote Procedure Call (RPC) services. It is typically used to develop network-accessible backends, APIs, or edge services that require fast, low-latency communication and efficient handling of high-throughput streaming data between distributed systems.

What does CVE-2026-78334 mean by missing authentication?

This vulnerability, classified as CWE-306 (Missing Authentication for Critical Function), means the software fails to verify the identity of a peer during certain streaming communications. Even if you have configured authentication on your server, the streaming RPC path bypasses those checks, allowing unauthenticated remote parties to interact with the service as if they were authorized.

Does my bRPC server trigger this if authentication is off?

No. The vulnerability specifically affects servers where authentication is already configured. If you do not use authentication for your streaming RPCs, the technical flaw—which involves frames bypassing the intended authentication hook—does not apply because there is no mechanism being bypassed in that configuration.

How do I know if my systems are reachable for this threat?

According to Halo Surface Signal, this vulnerability is particularly relevant for services deployed as network-accessible backends or edge services. If your bRPC-based application is configured with authentication and is reachable from an untrusted network segment, it is susceptible to unauthorized streaming frame injection.

What steps should I take to address this CVE?

Begin by identifying all deployments using Apache bRPC versions prior to 1.18.0. Determine which of these servers utilize streaming RPCs and are exposed to untrusted networks. Once identified, prioritize updating to version 1.18.0 or applying the provided patch to ensure streaming frames are correctly validated and bound to the proper communication sockets.

References

lists.apache.org/thread/2pf15ojj0vr7rtx95677kgtl1mx3gdgb

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.