Description

Incorrect Authorization (CWE-863) in Fleet Server can lead to a denial of service of agent upload operations via Privilege Abuse (CAPEC-122). Fleet Server does not correctly verify session ownership during multi-part data upload operations, allowing any authenticated agent to interfere with the active upload sessions belonging to other enrolled agents.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "3.1",
  "pubDate": "2026-09-02T15:17:40.190Z",
  "pubdate": "2026-09-02T15:17:40.190Z",
  "executiveSummary": "This vulnerability, identified as CWE-863 (Incorrect Authorization), affects Fleet Server and concerns the integrity of agent upload operations. The flaw stems from a failure to validate session ownership during multi-part data transfer sequences, facilitating Privilege Abuse (CAPEC-122).\nThe vulnerability allows an authenticated agent to interfere with or disrupt active upload sessions belonging to other enrolled agents within the Fleet architecture. By leveraging this lack of session verification, an attacker can perform a Denial of Service (DoS) against legitimate data ingestion processes. The risk implication involves the potential for data loss or service disruption for specific agents, impacting the overall reliability and observability of the fleet management infrastructure.\nExploitation requires the attacker to hold valid agent credentials, as the vulnerability is restricted to authenticated entities within the environment. No further privilege escalation beyond valid agent-level access is required, as the flaw lies in the server-side logic governing session state management rather than agent-side permissions.",
  "technicalDetails": "The root cause of this vulnerability is an authorization logic error within the Fleet Server's handling of multi-part data upload operations. Specifically, the server fails to enforce strict ownership verification for upload sessions. In a typical architecture, a session ID associated with an upload should be cryptographically bound to the identity of the initiating agent; however, the Fleet Server does not perform this validation during subsequent parts of the multi-part upload process.\nThe attack flow proceeds as follows: First, a legitimate agent initiates a multi-part upload session to the Fleet Server. The server grants the agent a session identifier. Second, an authenticated malicious agent, aware of or guessing the active session identifier, sends specially crafted upload requests targeting that same session ID. Because the server lacks session-to-agent binding verification, it accepts the malicious packets as part of the established session.\nBy injecting data into or prematurely terminating another agent's active session, the attacker can corrupt the upload payload or force the server to discard the transfer, effectively achieving a Denial of Service. The vulnerability resides within the session management middleware of the Fleet Server component, which processes these requests without verifying the request's origin against the session's recorded ownership.\nThis behavior constitutes a clear case of privilege abuse, as the system erroneously grants agents the implicit authority to modify or interact with state objects (the upload sessions) belonging to other distinct entities. The impact is primarily a targeted DoS, which may be leveraged to prevent security telemetry from reaching the backend, potentially blinding security operations centers to activity occurring on the victim agent's host. The exploitation surface is restricted to the network interface where the Fleet Server accepts agent communications, and because it requires an active, authenticated session, it does not allow for unauthorized entry but does allow for the subversion of the existing protocol flow between the agent and the server."
}