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BREW-COPYPARTY-CVE-2026-27448 (GHSA-VP96-HXJ8-P424)

Vulnerability from osv_homebrew – Published: 2026-08-13 16:41 – Updated: 2026-09-17 17:43 – Source website
VLAI
Summary
pyOpenSSL allows TLS connection bypass via unhandled callback exception in set_tlsext_servername_callback
Details

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.

Unhandled exceptions now result in rejecting the connection.

Credit to Leury Castillo for reporting this issue.

Severity
1.7 (Low)
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "pyopenssl",
        "resource_purl": "pkg:pypi/pyopenssl@26.4.0",
        "upstream_fixed_in": "26.0.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "copyparty",
        "purl": "pkg:brew/copyparty"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.18.6"
            },
            {
              "fixed": "1.20.12_1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/pyopenssl@26.4.0",
        "name": "pyopenssl",
        "resource": "pyopenssl",
        "strategy": "registry",
        "subject_version": "26.4.0"
      }
    ]
  },
  "details": "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.\n\nUnhandled exceptions now result in rejecting the connection.\n\nCredit to **Leury Castillo** for reporting this issue.",
  "id": "BREW-copyparty-CVE-2026-27448",
  "modified": "2026-09-17T17:43:18Z",
  "published": "2026-08-13T16:41:06Z",
  "references": [
    {
      "type": "WEB",
      "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": "WEB",
      "url": "https://github.com/pyca/pyopenssl/commit/d41a814759a9fb49584ca8ab3f7295de49a85aa0"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/pyca/pyopenssl"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst#L27"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U",
      "type": "CVSS_V4"
    }
  ],
  "summary": "pyOpenSSL allows TLS connection bypass via unhandled callback exception in set_tlsext_servername_callback",
  "upstream": [
    "GHSA-vp96-hxj8-p424",
    "CVE-2026-27448",
    "PYSEC-2026-2268"
  ]
}



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