# CVE-2025-27621: UpTrain has a Constant Default API Key

> Attackers can use a static default API key and open CORS policy to perform privileged operations on UpTrain instances from arbitrary websites.

- **Severity:** High 7.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 17 Aug 2026
- **Updated:** 17 Aug 2026

## What is CVE-2025-27621?

CVE-2025-27621 is a high-severity vulnerability in uptrain-ai uptrain, published on 17 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

UpTrain is an open-source platform to evaluate and improve generative AI applications. In version 0.7.1 and prior, the UpTrain backend creates a new default user with a static username, where the username is also used as the default API key. The UpTrain backend also has an open CORS policy. Using these two primitives, any website can make a authenticated cross-origin request to the UpTrain instance by providing the default API key in the header `uptrain-access-token`. This issue may allow arbitrary websites to perform privileged operations on the UpTrain instance, as if they were the default logged in user. As of time of publication, no known patches are available.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2025-27621?


## How do I fix CVE-2025-27621?

No fix has been published for CVE-2025-27621 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-27621 being exploited?

There is no known exploitation of CVE-2025-27621 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-27621 and fix it if it is affected.

What it is: CVE-2025-27621 is a high-severity vulnerability in uptrain-ai uptrain, published on 17 Aug 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-2025-27621 in the wild and no public exploit code.

Affected product: uptrain-ai uptrain. 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-2025-27621/ (Markdown: https://insights.sbomify.com/CVE-2025-27621/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-27621
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-27621
- OSV: https://osv.dev/vulnerability/CVE-2025-27621

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-27621/
Summaries are generated and may contain mistakes; the official description above is the record.