CVE-2022-31015

Uncaught Exception (due to a data race) leads to process termination in Waitress

Workarounds

There is no work-around, however users using waitress behind a reverse proxy server are less likely to have issues if the reverse proxy always reads the full response.

For more information

If you have any questions or comments about this advisory:

• Open an issue in https://github.com/Pylons/waitress/issues (if not sensitive or security related)
• email the Pylons Security mailing list: [email protected] (if security related)

Waitress may terminate early due to a thread closing a socket while the main thread is about to call select(). This will lead to the main thread raising an exception that is not handled and then causing the entire application to be killed.

Multiple concurrent operations access a shared resource without proper synchronization, producing unpredictable results depending on timing. Typical impact: TOCTOU exploits, data corruption, or privilege escalation.

CVE-2022-31015 has a CVSS score of 6.5 (High). The vector is network-reachable, low 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 (2.1.2); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

This issue has been fixed in Waitress 2.1.2 by no longer allowing the WSGI thread to close the socket, instead it is always delegated to the main thread.

1. What is CVE-2022-31015? CVE-2022-31015 is a high-severity race condition vulnerability in waitress (pip), affecting versions >= 2.1.0, < 2.1.2. It is fixed in 2.1.2. Multiple concurrent operations access a shared resource without proper synchronization, producing unpredictable results depending on timing.
2. How severe is CVE-2022-31015? CVE-2022-31015 has a CVSS score of 6.5 (High). 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 waitress are affected by CVE-2022-31015? waitress (pip) versions >= 2.1.0, < 2.1.2 is affected.
4. Is there a fix for CVE-2022-31015? Yes. CVE-2022-31015 is fixed in 2.1.2. Upgrade to this version or later.
5. Is CVE-2022-31015 exploitable, and should I be worried? Whether CVE-2022-31015 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-2022-31015 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-2022-31015? Upgrade waitress to 2.1.2 or later.

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