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BREW-ABI3AUDIT-CVE-2021-28363 (GHSA-5PHF-PP7P-VC2R)

Vulnerability from osv_homebrew – Published: 2026-08-13 16:34 – Updated: 2026-09-10 18:49 – Source website
VLAI
Summary
Using default SSLContext for HTTPS requests in an HTTPS proxy doesn't verify certificate hostname for proxy connection
Details

Impact

Users who are using an HTTPS proxy to issue HTTPS requests and haven't configured their own SSLContext via proxy_config. Only the default SSLContext is impacted.

Patches

urllib3 >=1.26.4 has the issue resolved. urllib3<1.26 is not impacted due to not supporting HTTPS requests via HTTPS proxies.

Workarounds

Upgrading is recommended as this is a minor release and not likely to break current usage.

Configuring an SSLContext with check_hostname=True and passing via proxy_config instead of relying on the default SSLContext

For more information

If you have any questions or comments about this advisory: * Email us at sethmichaellarson@gmail.com

Severity
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
6.9 (Medium)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "urllib3",
        "resource_purl": "pkg:pypi/urllib3@2.7.0",
        "upstream_fixed_in": "1.26.4"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "abi3audit",
        "purl": "pkg:brew/abi3audit"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.0.26_4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/urllib3@2.7.0",
        "name": "urllib3",
        "resource": "urllib3",
        "strategy": "registry",
        "subject_version": "2.7.0"
      }
    ]
  },
  "details": "### Impact\n\nUsers who are using an HTTPS proxy to issue HTTPS requests and haven\u0027t configured their own SSLContext via `proxy_config`.\nOnly the default SSLContext is impacted.\n\n### Patches\n\n[urllib3 \u003e=1.26.4 has the issue resolved](https://github.com/urllib3/urllib3/releases/tag/1.26.4). urllib3\u003c1.26 is not impacted due to not supporting HTTPS requests via HTTPS proxies.\n\n### Workarounds\n\nUpgrading is recommended as this is a minor release and not likely to break current usage.\n\nConfiguring an `SSLContext` with `check_hostname=True` and passing via `proxy_config` instead of relying on the default `SSLContext`\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Email us at [sethmichaellarson@gmail.com](mailto:sethmichaellarson@gmail.com)",
  "id": "BREW-abi3audit-CVE-2021-28363",
  "modified": "2026-09-10T18:49:43Z",
  "published": "2026-08-13T16:34:56Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/urllib3/urllib3/security/advisories/GHSA-5phf-pp7p-vc2r"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-28363"
    },
    {
      "type": "WEB",
      "url": "https://github.com/urllib3/urllib3/commit/8d65ea1ecf6e2cdc27d42124e587c1b83a3118b0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/urllib3/PYSEC-2021-59.yaml"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-db/tree/main/vulns/urllib3/PYSEC-2021-59.yaml"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/urllib3/urllib3"
    },
    {
      "type": "WEB",
      "url": "https://github.com/urllib3/urllib3/blob/main/CHANGES.rst#1264-2021-03-15"
    },
    {
      "type": "WEB",
      "url": "https://github.com/urllib3/urllib3/commits/main"
    },
    {
      "type": "WEB",
      "url": "https://github.com/urllib3/urllib3/releases/tag/1.26.4"
    },
    {
      "type": "WEB",
      "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4S65ZQVZ2ODGB52IC7VJDBUK4M5INCXL"
    },
    {
      "type": "WEB",
      "url": "https://pypi.org/project/urllib3/1.26.4"
    },
    {
      "type": "WEB",
      "url": "https://security.gentoo.org/glsa/202107-36"
    },
    {
      "type": "WEB",
      "url": "https://security.gentoo.org/glsa/202305-02"
    },
    {
      "type": "WEB",
      "url": "https://security.netapp.com/advisory/ntap-20240621-0007"
    },
    {
      "type": "WEB",
      "url": "https://www.oracle.com/security-alerts/cpuoct2021.html"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Using default SSLContext for HTTPS requests in an HTTPS proxy doesn\u0027t verify certificate hostname for proxy connection",
  "upstream": [
    "GHSA-5phf-pp7p-vc2r",
    "CVE-2021-28363",
    "PYSEC-2021-59"
  ]
}



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