Auth bypass in Microsoft Ufo

CVE-2026-55440

Microsoft UFO open-source framework for intelligent automation across devices and platforms. Prior to 3.0.7, the COMMAND_RESULTS handler in ufo/server/ws/handler.py called get_or_create_session in ufo/server/services/session_manager.py without owner_client_id, allowing an authenticated client to create an unowned attacker-chosen session_id such as constellation_task_id = f"{task_name}@{task_id}" and deny the legitimate owner or exhaust memory with phantom sessions. This issue is fixed in version 3.0.7.

Vulnerability class: DoS (Denial of Service)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.013 (69.2th percentile), scored .

Low probability of exploitation in the next 30 days, but still tracked. 69th percentile — 69.2% 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-2026-55440: held from 0.013 to 0.013.

EPSS over last 30 days · oldest: 0.013 · newest: 0.013 · change: 0.000

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-55440?
CVE-2026-55440 is a medium-severity vulnerability in Microsoft Ufo, classified under Uncontrolled Resource Consumption. CVSS score: 6.5/10. Published 2026-07-16.
How severe is CVE-2026-55440?
Medium severity. CVSS v3 base score is 6.5 out of 10.