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Vulnerability record · CVE-2021-21240 · published 8 February 2021

CVE-2021-21240: Httplib2 project httplib2 uncontrolled resource consumption vulnerability

HHttplib2 Project · Httplib2

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.

7.5 CVSS 3.1 High EPSS 3.6% · top 10.9% CWE-400 · Uncontrolled resource consumption
7.5CVSS 3.1 base score, v2 5.0
3.6%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
8References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/httplib2/httplib2/commit/bd9ee252c8f099608019709e22c0d705e98d26bc PatchThird Party Advisory
https://github.com/httplib2/httplib2/pull/182 PatchThird Party Advisory
https://github.com/httplib2/httplib2/security/advisories/GHSA-93xj-8mrv-444m ExploitMitigationThird Party Advisory
https://pypi.org/project/httplib2 ProductThird Party Advisory
https://github.com/httplib2/httplib2/commit/bd9ee252c8f099608019709e22c0d705e98d26bc PatchThird Party Advisory
https://github.com/httplib2/httplib2/pull/182 PatchThird Party Advisory
https://github.com/httplib2/httplib2/security/advisories/GHSA-93xj-8mrv-444m ExploitMitigationThird Party Advisory
https://pypi.org/project/httplib2 ProductThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-21240), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.