CVE-2021-21240: HTTPLIB2 Project HTTPLIB2

High severity, CVSS 7.5. EPSS: 3.6% chance of exploitation in the next 30 days.

httplib2 is a comprehensive HTTP client library for Python. In httplib2 before version 0.19.0, a malicious server which responds with long series of "\xa0" characters in the "www-authenticate" header may cause Denial of Service (CPU burn while parsing header) of the httplib2 client accessing said server. This is fixed in version 0.19.0 which contains a new implementation of auth headers parsing using the pyparsing library.

Affected products

• HTTPLIB2 Project HTTPLIB2: before 0.19.0 (fixed in 0.19.0)

Published 2021-02-08. Last modified 2026-06-17.