Vulnerability in Microsoft Ufo

CVE-2026-46538

Microsoft UFO open-source framework for intelligent automation across devices and platforms. In 3.0.1-4-ge2626659, Microsoft UFO's constellation client tracks pending task responses by session_id only and does not verify that a TASK_END message came from the device that originally received the task. When the constellation sends a task to a target device, it records a pending Future under a session key. The pending task record stores the expected device ID, but the completion path ignores that binding. If another authenticated peer device sends a forged TASK_END with the same session_id, the constellation accepts the response and completes the victim device's pending Future with attacker-controlled result data. This is an authenticated cross-device task-result injection issue.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:L.

EPSS exploit prediction

EPSS: 0.003 (20.8th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 21st percentile — 20.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-46538: held from 0.002 to 0.003.

EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-46538?
CVE-2026-46538 is a medium-severity vulnerability in Microsoft Ufo, classified under Authentication Bypass by Capture-replay. CVSS score: 5.9/10. Published 2026-05-27.
How severe is CVE-2026-46538?
Medium severity. CVSS v3 base score is 5.9 out of 10.