PYSEC-2026-3387

Vulnerability from pysec - Published: 2026-07-13 15:46 - Updated: 2026-07-13 16:07
VLAI
Details

Summary

When SimpleAsyncHTTPClient follows a 3xx redirect, it shallow-copies the original HTTPRequest, rewrites the URL, decrements max_redirects, and removes only the Host header. It does not clear Authorization, auth_username, auth_password, or auth_mode when the redirect target changes origin.

As a result, credentials intended for one origin can be forwarded to a different origin when follow_redirects=True, which is the default.

Beginning in Tornado 6.5.6, SimpleAsyncHTTPClient matches the default behavior of libcurl (and therefore CurlAsyncHTTPClient): When a redirect changes the scheme, host, or port of the url, the Authorization and Cookie headers will be removed when following the redirect.

Severity
7.7 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
Impacted products
Name purl
tornado pkg:pypi/tornado
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "tornado",
        "purl": "pkg:pypi/tornado"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.5.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.2",
        "1.0",
        "1.1",
        "1.1.1",
        "1.2",
        "1.2.1",
        "2.0",
        "2.1",
        "2.1.1",
        "2.2",
        "2.2.1",
        "2.3",
        "2.4",
        "2.4.1",
        "3.0",
        "3.0.1",
        "3.0.2",
        "3.1",
        "3.1.1",
        "3.2",
        "3.2.1",
        "3.2.2",
        "4.0",
        "4.0.1",
        "4.0.2",
        "4.1",
        "4.1b2",
        "4.2",
        "4.2.1",
        "4.2b1",
        "4.3",
        "4.3b1",
        "4.3b2",
        "4.4",
        "4.4.1",
        "4.4.2",
        "4.4.3",
        "4.4b1",
        "4.5",
        "4.5.1",
        "4.5.2",
        "4.5.3",
        "4.5b1",
        "4.5b2",
        "5.0",
        "5.0.1",
        "5.0.2",
        "5.0a1",
        "5.0b1",
        "5.1",
        "5.1.1",
        "5.1b1",
        "6.0",
        "6.0.1",
        "6.0.2",
        "6.0.3",
        "6.0.4",
        "6.0a1",
        "6.0b1",
        "6.1",
        "6.1b1",
        "6.1b2",
        "6.2",
        "6.2b1",
        "6.2b2",
        "6.3",
        "6.3.1",
        "6.3.2",
        "6.3.3",
        "6.3b1",
        "6.4",
        "6.4.1",
        "6.4.2",
        "6.4b1",
        "6.5",
        "6.5.1",
        "6.5.2",
        "6.5.3",
        "6.5.4",
        "6.5.5",
        "6.5b1"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-49853",
    "GHSA-3x9g-8vmp-wqvf"
  ],
  "details": "## Summary\n\nWhen SimpleAsyncHTTPClient follows a 3xx redirect, it shallow-copies the original HTTPRequest, rewrites the URL, decrements max_redirects, and removes only the Host header. It does not clear Authorization, auth_username, auth_password, or auth_mode when the redirect target changes origin.\n\nAs a result, credentials intended for one origin can be forwarded to a different origin when follow_redirects=True, which is the default.\n\nBeginning in Tornado 6.5.6, `SimpleAsyncHTTPClient` matches the default behavior of `libcurl` (and therefore `CurlAsyncHTTPClient`): When a redirect changes the scheme, host, or port of the url, the `Authorization` and `Cookie` headers will be removed when following the redirect.",
  "id": "PYSEC-2026-3387",
  "modified": "2026-07-13T16:07:18.823449Z",
  "published": "2026-07-13T15:46:17.169568Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-3x9g-8vmp-wqvf"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/tornadoweb/tornado"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/tornado"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-3x9g-8vmp-wqvf"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-49853"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Tornado: Authorization header forwarded across cross-origin redirects in SimpleAsyncHTTPClient"
}



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