{"id":"CVE-2019-16791","aliases":["GHSA-h92m-42h4-82f6","PYSEC-2020-174"],"url":"https://o3.security/vulnerability/CVE-2019-16791","summary":"postfix-mta-sts-resolver Algorithm Downgrade vulnerability","details":"## Incorrect query parsing\n\n### Impact\nAll users of versions prior to 0.5.1 can receive incorrect response from daemon under rare conditions, rendering downgrade of effective STS policy.\n\n### Patches\nProblem has been patched in version 0.5.1\n\n### Workarounds\nUsers may remediate this vulnerability without upgrading by applying [these patches](https://gist.github.com/Snawoot/b9da85d6b26dea5460673b29df1adc6b) to older suppoorted versions.\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in [postfix-mta-sts-resolver repo](https://github.com/Snawoot/postfix-mta-sts-resolver)\n* Email me at [vladislav at vm-0 dot com](mailto:vladislav-ex-gh-advisory@vm-0.com)","published":"2020-01-22T02:15:11.367Z","modified":"2026-10-20T10:51:37.997798771Z","cvss":{"score":5.9,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"postfix-mta-sts-resolver","fixedVersion":"0.5.1"}],"fix":null,"references":[{"type":"FIX","url":"https://gist.github.com/Snawoot/b9da85d6b26dea5460673b29df1adc6b"},{"type":"FIX","url":"https://github.com/Snawoot/postfix-mta-sts-resolver/security/advisories/GHSA-h92m-42h4-82f6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2019-16791"},{"type":"PACKAGE","url":"https://github.com/Snawoot/postfix-mta-sts-resolver"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/postfix-mta-sts-resolver/PYSEC-2020-174.yaml"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-20T10:51:37.997798771Z"}}