# CVE-2026-0773: Upsonic Cloudpickle Deserialization of Untrusted Data Remote Code Execution Vulnerability

> Remote attackers can execute arbitrary code via untrusted data deserialization in the add_tool endpoint without authentication.

- **Severity:** Critical 9.8 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 23 Jan 2026
- **Updated:** 23 Jan 2026
- **Also known as:** GHSA-8rrj-mw9c-258v

## What is CVE-2026-0773?

CVE-2026-0773 is a critical unsafe deserialization vulnerability in Upsonic, published on 23 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Upsonic Cloudpickle Deserialization of Untrusted Data Remote Code Execution Vulnerability. This vulnerability allows remote attackers to execute arbitrary code on affected installations of Upsonic. Authentication is not required to exploit this vulnerability.

The specific flaw exists within the add_tool endpoint, which listens on TCP port 7541 by default. The issue results from the lack of proper validation of user-supplied data, which can result in deserialization of untrusted data. An attacker can leverage this vulnerability to execute code in the context of the service account. Was ZDI-CAN-26845.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2026-0773?


## How do I fix CVE-2026-0773?

No fix has been published for CVE-2026-0773 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-0773 being exploited?

There is no known exploitation of CVE-2026-0773 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-0773 and fix it if it is affected.

What it is: CVE-2026-0773 is a critical unsafe deserialization vulnerability in Upsonic, published on 23 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-0773 in the wild and no public exploit code.

Affected product: Upsonic. 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-2026-0773/ (Markdown: https://insights.sbomify.com/CVE-2026-0773/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-0773
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-0773
- OSV: https://osv.dev/vulnerability/CVE-2026-0773

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-0773/
Summaries are generated and may contain mistakes; the official description above is the record.