{"id":"CVE-2026-27448","aliases":["GHSA-vp96-hxj8-p424","PYSEC-2026-2268"],"url":"https://o3.security/vulnerability/CVE-2026-27448","summary":"pyOpenSSL allows TLS connection bypass via unhandled callback exception in set_tlsext_servername_callback","details":"pyOpenSSL is a Python wrapper around the OpenSSL library. Starting in version 0.14.0 and prior to version 26.0.0, if a user provided callback to `set_tlsext_servername_callback` raised an unhandled exception, this would result in a connection being accepted. If a user was relying on this callback for any security-sensitive behavior, this could allow bypassing it. Starting in version 26.0.0, unhandled exceptions now result in rejecting the connection.","published":"2026-03-17T23:24:30.661Z","modified":"2026-09-06T03:45:30.230958341Z","cvss":null,"epss":{"score":0.00241,"percentile":0.1548,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"pyopenssl","fixedVersion":"26.0.0"}],"fix":{"url":"https://github.com/pyca/pyopenssl/commit/d41a814759a9fb49584ca8ab3f7295de49a85aa0","label":"pyca/pyopenssl@d41a814"},"references":[{"type":"WEB","url":"https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst#L27"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27448.json"},{"type":"ADVISORY","url":"https://github.com/pyca/pyopenssl/security/advisories/GHSA-vp96-hxj8-p424"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-27448"},{"type":"FIX","url":"https://github.com/pyca/pyopenssl/commit/d41a814759a9fb49584ca8ab3f7295de49a85aa0"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-06T03:45:30.230958341Z"}}