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CVE-2026-19445

Status: Awaiting AnalysisCritical (9.2)—

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.

CVSS

Exploitation probability (EPSS)

FIRST hasn't scored this CVE yet (usual for very recent or rejected CVEs).

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

Python — PythonAI

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2026-19445",
  "cveTags": [],
  "metrics": {
    "cvssMetricV40": [
      {
        "type": "Secondary",
        "source": "cna@python.org",
        "cvssData": {
          "Safety": "NOT_DEFINED",
          "version": "4.0",
          "Recovery": "NOT_DEFINED",
          "baseScore": 9.2,
          "Automatable": "NOT_DEFINED",
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "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",
          "exploitMaturity": "NOT_DEFINED",
          "providerUrgency": "NOT_DEFINED",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "attackRequirements": "PRESENT",
          "privilegesRequired": "NONE",
          "subIntegrityImpact": "NONE",
          "vulnIntegrityImpact": "HIGH",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "vulnAvailabilityImpact": "LOW",
          "availabilityRequirement": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "subConfidentialityImpact": "NONE",
          "vulnConfidentialityImpact": "HIGH",
          "confidentialityRequirement": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED"
        }
      }
    ]
  },
  "affected": [
    {
      "source": "cna@python.org",
      "affectedData": [
        {
          "repo": "https://github.com/python/cpython",
          "vendor": "Python Software Foundation",
          "modules": [
            "ssl"
          ],
          "product": "CPython",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "lessThan": "3.12.15",
              "versionType": "python"
            },
            {
              "status": "affected",
              "version": "3.13.0",
              "lessThan": "3.13.16",
              "versionType": "python"
            },
            {
              "status": "affected",
              "version": "3.14.0",
              "lessThan": "3.14.8",
              "versionType": "python"
            },
            {
              "status": "affected",
              "version": "3.15.0a1",
              "lessThan": "3.15.0",
              "versionType": "python"
            }
          ],
          "defaultStatus": "unaffected"
        }
      ]
    }
  ],
  "published": "2026-09-30T17:16:45.720",
  "references": [
    {
      "url": "https://github.com/python/cpython/commit/34a53dce8174da2fceb12fe084a4def02a10053d",
      "source": "cna@python.org"
    },
    {
      "url": "https://github.com/python/cpython/commit/46133cd57d309652139ada74014aca7665ac552b",
      "source": "cna@python.org"
    },
    {
      "url": "https://github.com/python/cpython/commit/63fab143d94cafae71850831acfb52041ba44af7",
      "source": "cna@python.org"
    },
    {
      "url": "https://github.com/python/cpython/commit/b12968cefe69ca1dcb8606c832ff73ee7dbf4ba8",
      "source": "cna@python.org"
    },
    {
      "url": "https://github.com/python/cpython/commit/cd7e51e7d4563866fbaa1e2521ae69b45daf3698",
      "source": "cna@python.org"
    },
    {
      "url": "https://github.com/python/cpython/commit/d8717ed01717a9641686e6e6f83f0ab8af235e2c",
      "source": "cna@python.org"
    },
    {
      "url": "https://github.com/python/cpython/commit/ec44b5a3258cbda947d5e07242ee562ed05ef24b",
      "source": "cna@python.org"
    },
    {
      "url": "https://github.com/python/cpython/issues/156293",
      "source": "cna@python.org"
    },
    {
      "url": "https://github.com/python/cpython/pull/158504",
      "source": "cna@python.org"
    },
    {
      "url": "https://mail.python.org/archives/list/security-announce@python.org/thread/QMQIUQB6WGGC3MI7I3WKQXOYOBDSPPS3/",
      "source": "cna@python.org"
    },
    {
      "url": "http://www.openwall.com/lists/oss-security/2026/09/30/17",
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "cna@python.org",
      "description": [
        {
          "lang": "en",
          "value": "CWE-416"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "A remote, unauthenticated TLS client can make a server crash or call\nthrough a freed pointer if its sni_callback assigns a different context to\nSSLSocket.context (the documented way to select a certificate per server\nname) and nothing else keeps the original ssl.SSLContext alive. Typical\ncases are servers that create an SSLContext per connection or replace it\nwhile connections are open; servers that wrap their listening socket with\nit are not affected.\n\n\nMitigation: keep a reference to every SSLContext that sets sni_callback for\nthe lifetime of the server. TLS clients are not affected."
    }
  ],
  "lastModified": "2026-10-01T01:16:36.590",
  "sourceIdentifier": "cna@python.org"
}