CVE-2026-46538 Overview
CVE-2026-46538 affects Microsoft UFO, an open-source framework for intelligent automation across devices and platforms. The vulnerability exists in the constellation client, which tracks pending task responses by session_id only. The client does not verify that a TASK_END message originates from the device that received the task. An authenticated peer device can forge a TASK_END message containing the same session_id and inject attacker-controlled result data into another device's pending Future. The flaw is classified under [CWE-294] Authentication Bypass by Capture-replay and represents a cross-device task-result injection issue in version 3.0.1-4-ge2626659.
Critical Impact
Any authenticated peer can hijack task completions across devices, corrupting automation results and influencing downstream actions taken by the victim device.
Affected Products
- Microsoft UFO open-source framework
- Version 3.0.1-4-ge2626659
- Constellation client component
Discovery Timeline
- 2026-05-27 - CVE-2026-46538 published to NVD
- 2026-05-27 - Last updated in NVD database
Technical Details for CVE-2026-46538
Vulnerability Analysis
The Microsoft UFO constellation coordinates task distribution and completion across multiple authenticated peer devices. When the constellation dispatches a task to a target device, it records a pending Future keyed by session_id. The pending task record also stores the expected device identifier responsible for completing that task.
The completion path ignores the device-binding portion of the record. When a TASK_END message arrives, the constellation matches the message only against the session_id and resolves the pending Future with whatever result payload is attached. Any authenticated peer device participating in the constellation can craft a TASK_END message containing the session_id of another device's in-flight task.
The attacker does not need to compromise the legitimate target device. The forged completion is accepted as authoritative, and downstream consumers of the result act on attacker-controlled data.
Root Cause
The root cause is incomplete authentication of the response sender. The pending task structure carries the expected device ID, but the message-handling logic does not enforce that binding when accepting TASK_END events. This is a missing authorization check on an authenticated channel, mapped to [CWE-294].
Attack Vector
An attacker must already hold valid credentials as a peer device within the constellation. From that position, the attacker observes or guesses an active session_id and sends a forged TASK_END carrying chosen result data. The constellation accepts the forged response, completes the victim's pending Future, and propagates the attacker-controlled result into the automation workflow.
No verified public exploit code is available. See the GitHub Security Advisory GHSA-wmq2-74rj-7pjc for vendor technical details.
Detection Methods for CVE-2026-46538
Indicators of Compromise
- Multiple TASK_END messages observed for the same session_id from different peer device identifiers.
- TASK_END events arriving from a device ID that does not match the dispatch record for that session.
- Anomalous task results that conflict with the executing device's local logs or telemetry.
Detection Strategies
- Correlate dispatched task records with completion events and alert when the sender device ID diverges from the expected target.
- Instrument the constellation client to log both session_id and originating device ID for every TASK_END and review for mismatches.
- Baseline normal task completion latency and result formats so injected payloads with abnormal structure surface during review.
Monitoring Recommendations
- Capture constellation message traces with sender identity preserved for forensic replay.
- Forward UFO automation logs to a centralized logging pipeline and alert on duplicate session completions.
- Audit peer device enrollment to ensure only trusted endpoints can authenticate to the constellation.
How to Mitigate CVE-2026-46538
Immediate Actions Required
- Upgrade Microsoft UFO to a release that supersedes 3.0.1-4-ge2626659 once a fixed version is published.
- Restrict constellation peer membership to the minimum set of trusted, hardened devices.
- Rotate any credentials used by peer devices that may have been exposed to untrusted operators.
Patch Information
Refer to the Microsoft UFO GitHub Security Advisory GHSA-wmq2-74rj-7pjc for the authoritative fix details and any patched release tags.
Workarounds
- Segment the constellation network so that only vetted devices can authenticate as peers.
- Apply application-level controls that validate the sender device ID against the pending task record before accepting TASK_END.
- Reduce blast radius by scoping each constellation to small device groups instead of one large shared session pool.
# Configuration example
# Review GHSA-wmq2-74rj-7pjc for the official remediation guidance.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
