{"id":"CVE-2021-21240","aliases":["GHSA-93xj-8mrv-444m","PYSEC-2021-16"],"url":"https://o3.security/vulnerability/CVE-2021-21240","summary":"Regular Expression Denial of Service (REDoS) in httplib2","details":"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.","published":"2021-02-08T20:15:12.197Z","modified":"2026-07-09T10:14:55.748879842Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":{"score":0.03983,"percentile":0.89735,"asOf":"2026-08-23"},"cisaKev":null,"exploitsKnown":1,"affectedPackages":[{"ecosystem":"PyPI","name":"httplib2","fixedVersion":"0.19.0"}],"fix":{"url":"https://github.com/httplib2/httplib2/commit/bd9ee252c8f099608019709e22c0d705e98d26bc","label":"httplib2/httplib2@bd9ee25"},"references":[{"type":"FIX","url":"https://github.com/httplib2/httplib2/commit/bd9ee252c8f099608019709e22c0d705e98d26bc"},{"type":"FIX","url":"https://github.com/httplib2/httplib2/pull/182"},{"type":"PACKAGE","url":"https://pypi.org/project/httplib2"},{"type":"EVIDENCE","url":"https://github.com/httplib2/httplib2/security/advisories/GHSA-93xj-8mrv-444m"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-09T10:14:55.748879842Z"}}