CVE-2021-21240

Public Exploit
Regular Expression Denial of Service in httplib2

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.

Category

7.5
CVSS
Severity: High
CVSS 3.1 •
CVSS 2.0 •
EPSS 2.20% Top 20%
Third-Party Advisory github.com Third-Party Advisory github.com Third-Party Advisory github.com Third-Party Advisory pypi.org
Affected: httplib2 httplib2
Published at:
Updated at:

References

Link Tags
https://github.com/httplib2/httplib2/security/advisories/GHSA-93xj-8mrv-444m exploit third party advisory mitigation
https://github.com/httplib2/httplib2/pull/182 third party advisory patch
https://github.com/httplib2/httplib2/commit/bd9ee252c8f099608019709e22c0d705e98d26bc third party advisory patch
https://pypi.org/project/httplib2 third party advisory product

Frequently Asked Questions

What is the severity of CVE-2021-21240?
CVE-2021-21240 has been scored as a high severity vulnerability.
How to fix CVE-2021-21240?
To fix CVE-2021-21240, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2021-21240 being actively exploited in the wild?
It is possible that CVE-2021-21240 is being exploited or will be exploited in a near future based on public information. According to its EPSS score, there is a ~2% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2021-21240?
CVE-2021-21240 affects httplib2 httplib2.
This platform uses data from the NIST NVD, MITRE CVE, MITRE CWE, First.org and CISA KEV but is not endorsed or certified by these entities. CVE is a registred trademark of the MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. CWE is a registred trademark of the MITRE Corporation and the authoritative source of CWE content is MITRE's CWE web site.
© 2025 Under My Watch. All Rights Reserved.