CVE-2021-37705

Improper Authorization and Origin Validation Error in OneFuzz

Workarounds

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.

References

You can find an overview of the Microsoft Identity Platform here. This vulnerability applies to the multi-tenant application pattern, as described here.

For more information

If you have any questions or comments about this advisory:

• Open an issue in OneFuzz
• Email us at [email protected]

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:

• Version 2.12.0 or greater
• 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
• Proprietary code and symbols

Via authorized API calls, this also enables tampering with existing data and unauthorized code execution on Azure compute resources.

The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.

CVE-2021-37705 has a CVSS score of 10.0 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.31.0); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

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.

1. What is CVE-2021-37705? CVE-2021-37705 is a critical-severity incorrect authorization vulnerability in onefuzz (pip), affecting versions >= 2.12.0, < 2.31.0. It is fixed in 2.31.0. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
2. How severe is CVE-2021-37705? CVE-2021-37705 has a CVSS score of 10.0 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of onefuzz are affected by CVE-2021-37705? onefuzz (pip) versions >= 2.12.0, < 2.31.0 is affected.
4. Is there a fix for CVE-2021-37705? Yes. CVE-2021-37705 is fixed in 2.31.0. Upgrade to this version or later.
5. Is CVE-2021-37705 exploitable, and should I be worried? Whether CVE-2021-37705 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2021-37705 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2021-37705? Upgrade onefuzz to 2.31.0 or later.