CVE-2026-78334 Vulnerability Analysis & Exploit Details

CVE-2026-78334 Vulnerability Summary

CVE-2026-78334: Missing authentication in the streaming RPC path of Apache bRPC (version < 1.18.0) on all platforms allows a remote attacker to bypass server authentication and inject or deliver streaming frames, when a server is configured with an Authenticator. Root Cause: When authentication is configured, streaming RPC frames are consumed directly by the streaming parser (ParseStreamingMessage) and never pass through InputMessenger's authentication hook, so an unauthenticated peer can exchange frames without being authenticated. In addition, a server-accepted stream is bound lazily to the first frame that happens to carry its id, so a stream could accept a frame carrying its id from a socket other than the socket that created the stream. Affected Scenarios: A bRPC server configured with authentication that serves streaming RPC from an untrusted network, or a deployment where a foreign connection can impersonate a stream by id, can be made to accept unauthorized streaming frames. How to Fix: Upgrade bRPC to 1.18.0, which fixes this issue, or apply the patch in PR https://github.com/apache/brpc/pull/3481. Note: The fix rejects streaming frames on server sockets when configured authentication has not completed, and keeps server-accepted streams bound to the socket of their creating RPC and rejects frames arriving from another socket. Authenticated streaming RPC behavior and the wire format are unchanged; only unauthenticated or foreign-socket frames are now rejected.

CVE-2026-78334 References

External References

• https://lists.apache.org/thread/2pf15ojj0vr7rtx95677kgtl1mx3gdgb

CWE Common Weakness Enumeration

CAPEC Common Attack Pattern Enumeration and Classification

• Choosing Message Identifier CAPEC-12 This pattern of attack is defined by the selection of messages distributed via multicast or public information channels that are intended for another client by determining the parameter value assigned to that client. This attack allows the adversary to gain access to potentially privileged information, and to possibly perpetrate other attacks through the distribution means by impersonation. If the channel/message being manipulated is an input rather than output mechanism for the system, (such as a command bus), this style of attack could be used to change the adversary's identifier to more a privileged one.
• Force the System to Reset Values CAPEC-166 An attacker forces the target into a previous state in order to leverage potential weaknesses in the target dependent upon a prior configuration or state-dependent factors. Even in cases where an attacker may not be able to directly control the configuration of the targeted application, they may be able to reset the configuration to a prior state since many applications implement reset functions.
• Communication Channel Manipulation CAPEC-216 An adversary manipulates a setting or parameter on communications channel in order to compromise its security. This can result in information exposure, insertion/removal of information from the communications stream, and/or potentially system compromise.
• Using Unpublished Interfaces or Functionality CAPEC-36 An adversary searches for and invokes interfaces or functionality that the target system designers did not intend to be publicly available. If interfaces fail to authenticate requests, the attacker may be able to invoke functionality they are not authorized for.
• Cross Site Request Forgery CAPEC-62 An attacker crafts malicious web links and distributes them (via web pages, email, etc.), typically in a targeted manner, hoping to induce users to click on the link and execute the malicious action against some third-party application. If successful, the action embedded in the malicious link will be processed and accepted by the targeted application with the users' privilege level. This type of attack leverages the persistence and implicit trust placed in user session cookies by many web applications today. In such an architecture, once the user authenticates to an application and a session cookie is created on the user's system, all following transactions for that session are authenticated using that cookie including potential actions initiated by an attacker and simply "riding" the existing session cookie.

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