# CVE-2026-46538: Microsoft UFO accepts cross-device TASK_END messages by session_id only, allowing peer task-result injection

> An authenticated peer can inject forged task results into Microsoft UFO by spoofing session IDs, potentially compromising automation workflows.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 May 2026
- **Updated:** 28 May 2026

## What is CVE-2026-46538?

CVE-2026-46538 is a medium-severity missing authorization vulnerability in microsoft UFO, published on 27 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

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.

Weakness: CWE-345 (Insufficient Verification of Data Authenticity), CWE-294 (Authentication Bypass by Capture-replay)

## Which versions are affected by CVE-2026-46538?


## How do I fix CVE-2026-46538?

No fix has been published for CVE-2026-46538 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-46538 being exploited?

There is no known exploitation of CVE-2026-46538 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-46538 and fix it if it is affected.

What it is: CVE-2026-46538 is a medium-severity missing authorization vulnerability in microsoft UFO, published on 27 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-46538 in the wild and no public exploit code.

Affected product: microsoft UFO. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-46538/ (Markdown: https://insights.sbomify.com/CVE-2026-46538/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46538
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46538
- OSV: https://osv.dev/vulnerability/CVE-2026-46538

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46538/
Summaries are generated and may contain mistakes; the official description above is the record.