CVE-2022-31015: Uncaught Exception (due to a data race) leads to process termination in Waitress

Severity: medium (CVSS 5.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.5% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2022-05-31 · updated 2026-06-17
Weakness: CWE-248

Description

Waitress is a Web Server Gateway Interface server for Python 2 and 3. Waitress versions 2.1.0 and 2.1.1 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. This issue has been fixed in Waitress 2.1.2 by no longer allowing the WSGI thread to close the socket. Instead, that is always delegated to the main thread. There is no work-around for this issue. However, users using waitress behind a reverse proxy server are less likely to have issues if the reverse proxy always reads the full response.

Affected products

Pylons Waitress: from 2.1.0 before 2.1.2 — fixed in 2.1.2

How to fix

Upgrade to a fixed version: Pylons Waitress 2.1.2. Check the vendor advisory for mitigations.

References

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