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

Vulnerability summary

CVE-2022-31015 is a medium (CVSS 6.5) Uncaught Exception vulnerability in agendaless waitress. EPSS estimates a 1.50% chance of exploitation in the next 30 days, higher than 74.2% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 31-05-2022
   PublishedVulnerability first disclosed.
2. 22-04-2025
   Last modifiedVulnerability information updated.

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.

• CWE-248Uncaught ExceptionAn exception is thrown from a function, but it is not caught.
• CWE-362Concurrent Execution using Shared Resource with Improper SynchronizationThe product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.