{"cve":"CVE-2021-21240","nvd":{"published":"2021-02-08T20:15:12.197","modified":"2026-06-17T03:35:06.433","status":"Modified","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_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-400"],"references":["https://github.com/httplib2/httplib2/commit/bd9ee252c8f099608019709e22c0d705e98d26bc","https://github.com/httplib2/httplib2/pull/182","https://github.com/httplib2/httplib2/security/advisories/GHSA-93xj-8mrv-444m","https://pypi.org/project/httplib2","https://github.com/httplib2/httplib2/commit/bd9ee252c8f099608019709e22c0d705e98d26bc"],"products":["httplib2_project:httplib2"],"source":"nvd","synced_at":"2026-10-19T21:14:10.479542811+00:00"},"epss":{"cve":"CVE-2021-21240","score":0.03626,"percentile":0.8953,"date":"2026-11-01"},"kev":null,"osv":[{"id":"GHSA-93xj-8mrv-444m","url":"https://osv.dev/vulnerability/GHSA-93xj-8mrv-444m","summary":"Regular Expression Denial of Service (REDoS) in httplib2","modified":"2026-09-10T03:49:14.200521093Z","packages":[{"ecosystem":"PyPI","name":"httplib2","purl":"pkg:pypi/httplib2","ranges":["<0.19.0"],"fixed":["0.19.0"]}]},{"id":"PYSEC-2021-16","url":"https://osv.dev/vulnerability/PYSEC-2021-16","summary":"","modified":"2023-11-08T04:04:39.189613Z","packages":[{"ecosystem":"PyPI","name":"httplib2","purl":"pkg:pypi/httplib2","ranges":["<0.19.0"],"fixed":["0.19.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}