CVE-2021-37705: 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...

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.

Metrics

CVSS 3.1

10/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS Probability

2.42%

82.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Microsoft	Onefuzz	>= 2.12.0, < 2.31.0

References

https://github.com/microsoft/onefuzz/commit/2fcb4998887959b4fa11894a068d689189742cb1Patch, Third Party Advisory
https://github.com/microsoft/onefuzz/pull/1153Patch, Third Party Advisory
https://github.com/microsoft/onefuzz/releases/tag/2.31.0Release Notes, Third Party Advisory
https://github.com/microsoft/onefuzz/security/advisories/GHSA-q5vh-6whw-x745Third Party Advisory
https://pypi.org/project/onefuzz/Product
https://github.com/microsoft/onefuzz/commit/2fcb4998887959b4fa11894a068d689189742cb1Patch, Third Party Advisory
https://github.com/microsoft/onefuzz/pull/1153Patch, Third Party Advisory
https://github.com/microsoft/onefuzz/releases/tag/2.31.0Release Notes, Third Party Advisory
https://github.com/microsoft/onefuzz/security/advisories/GHSA-q5vh-6whw-x745Third Party Advisory
https://pypi.org/project/onefuzz/Product

Timeline

Published: Aug 13, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-37705?

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.

How severe is CVE-2021-37705?

CVE-2021-37705 has a CVSS score of 10/10 (CRITICAL severity). The EPSS model estimates a 2.42% probability of exploitation in the next 30 days.

How do I fix CVE-2021-37705?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.