Use-after-free of a server-side SSLContext when sni_callback switches contexts

{
  "id": "6314247a076bd4b79503126373cddde3bf2d22168a3bfec1f6eaf5a2fee1de4b",
  "url": "https://osv.dev/vulnerability/BIT-libpython-2026-19445",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Use-after-free of a server-side SSLContext when sni_callback switches contexts",
    "summary": "A remote, unauthenticated TLS client can make a server crash or call through a freed pointer if its sni_callback assigns a different context to SSLSocket.context (the documented way to select a certificate per server name) and nothing else keeps the original ssl.SSLContext alive. Typical cases are servers that create an SSLContext per connection or replace it while connections are open; servers that wrap their listening socket with it are not affected. Mitigation: keep a reference to every SSLContext that sets sni_callback for the lifetime of the server. TLS clients are not affected.",
    "evidence": "osv:BIT-libpython-2026-19445",
    "products": [
      {
        "name": {
          "value": "libpython",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "3.10.22",
            "evidence": "/affected/0/ranges"
          },
          {
            "value": "3.11.17",
            "evidence": "/affected/0/ranges"
          },
          {
            "value": "3.12.15",
            "evidence": "/affected/0/ranges"
          },
          {
            "value": "3.13.16",
            "evidence": "/affected/0/ranges"
          },
          {
            "value": "3.14.8",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "critical",
    "structured": {
      "id": "BIT-libpython-2026-19445",
      "aliases": [
        "BIT-libpython-2026-19445",
        "BIT-python-2026-19445",
        "BIT-python-min-2026-19445",
        "CVE-2026-19445",
        "PSF-2026-43"
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "3.10.22"
                },
                {
                  "introduced": "3.11.0"
                },
                {
                  "fixed": "3.11.17"
                },
                {
                  "introduced": "3.12.0"
                },
                {
                  "fixed": "3.12.15"
                },
                {
                  "introduced": "3.13.0"
                },
                {
                  "fixed": "3.13.16"
                },
                {
                  "introduced": "3.14.0"
                },
                {
                  "fixed": "3.14.8"
                }
              ]
            }
          ],
          "package": {
            "name": "libpython",
            "purl": "pkg:bitnami/libpython",
            "ecosystem": "Bitnami"
          },
          "severity": [
            {
              "type": "CVSS_V4",
              "score": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X"
            }
          ],
          "database_specific": {
            "source": "https://github.com/bitnami/vulndb/tree/main/data/libpython/BIT-libpython-2026-19445.json"
          }
        }
      ],
      "modified": "2026-10-09T12:10:32.528164652Z",
      "provider": "osv",
      "references": [
        "https://github.com/python/cpython/commit/34a53dce8174da2fceb12fe084a4def02a10053d",
        "https://github.com/python/cpython/commit/46133cd57d309652139ada74014aca7665ac552b",
        "https://github.com/python/cpython/commit/63fab143d94cafae71850831acfb52041ba44af7",
        "https://github.com/python/cpython/commit/b12968cefe69ca1dcb8606c832ff73ee7dbf4ba8",
        "https://github.com/python/cpython/commit/cd7e51e7d4563866fbaa1e2521ae69b45daf3698",
        "https://github.com/python/cpython/commit/d8717ed01717a9641686e6e6f83f0ab8af235e2c",
        "https://github.com/python/cpython/commit/ec44b5a3258cbda947d5e07242ee562ed05ef24b",
        "https://github.com/python/cpython/issues/156293",
        "https://github.com/python/cpython/pull/158504",
        "https://mail.python.org/archives/list/security-announce@python.org/thread/QMQIUQB6WGGC3MI7I3WKQXOYOBDSPPS3/",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-19445"
      ],
      "provider_metadata": {
        "cpes": [
          "cpe:2.3:a:python:python:*:*:*:*:*:*:*:*"
        ],
        "severity": "Critical"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-19445",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/database_specific/severity"
  },
  "source_id": "core-osv",
  "document_id": 120733,
  "published_at": "2026-10-09T10:48:12.092+00:00"
}