FKIE_CVE-2026-19445

Vulnerability from fkie_nvd - Published: 2026-09-30 17:16 - Updated: 2026-09-30 23:17
Severity
9.2 (Critical) - 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
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.
References
cna@python.orghttps://github.com/python/cpython/commit/34a53dce8174da2fceb12fe084a4def02a10053d
cna@python.orghttps://github.com/python/cpython/commit/46133cd57d309652139ada74014aca7665ac552b
cna@python.orghttps://github.com/python/cpython/commit/63fab143d94cafae71850831acfb52041ba44af7
cna@python.orghttps://github.com/python/cpython/commit/cd7e51e7d4563866fbaa1e2521ae69b45daf3698
cna@python.orghttps://github.com/python/cpython/commit/d8717ed01717a9641686e6e6f83f0ab8af235e2c
cna@python.orghttps://github.com/python/cpython/issues/156293
cna@python.orghttps://github.com/python/cpython/pull/158504
cna@python.orghttps://mail.python.org/archives/list/security-announce@python.org/thread/QMQIUQB6WGGC3MI7I3WKQXOYOBDSPPS3/
af854a3a-2127-422b-91ae-364da2661108http://www.openwall.com/lists/oss-security/2026/09/30/17
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "modules": [
            "ssl"
          ],
          "product": "CPython",
          "repo": "https://github.com/python/cpython",
          "vendor": "Python Software Foundation",
          "versions": [
            {
              "lessThan": "3.12.15",
              "status": "affected",
              "version": "0",
              "versionType": "python"
            },
            {
              "lessThan": "3.13.16",
              "status": "affected",
              "version": "3.13.0",
              "versionType": "python"
            },
            {
              "lessThan": "3.14.8",
              "status": "affected",
              "version": "3.14.0",
              "versionType": "python"
            },
            {
              "lessThan": "3.15.0",
              "status": "affected",
              "version": "3.15.0a1",
              "versionType": "python"
            }
          ]
        }
      ],
      "source": "cna@python.org"
    }
  ],
  "cveTags": [],
  "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."
    }
  ],
  "id": "CVE-2026-19445",
  "lastModified": "2026-09-30T23:17:00.570",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "HIGH",
          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 9.2,
          "baseSeverity": "CRITICAL",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "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",
          "version": "4.0",
          "vulnAvailabilityImpact": "LOW",
          "vulnConfidentialityImpact": "HIGH",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "cna@python.org",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-30T17:16:45.720",
  "references": [
    {
      "source": "cna@python.org",
      "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/cd7e51e7d4563866fbaa1e2521ae69b45daf3698"
    },
    {
      "source": "cna@python.org",
      "url": "https://github.com/python/cpython/commit/d8717ed01717a9641686e6e6f83f0ab8af235e2c"
    },
    {
      "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": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "http://www.openwall.com/lists/oss-security/2026/09/30/17"
    }
  ],
  "sourceIdentifier": "cna@python.org",
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-416"
        }
      ],
      "source": "cna@python.org",
      "type": "Secondary"
    }
  ]
}



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