CVE-2024-37891: Urllib3 Urllib3's Proxy-Authorization Request Header Isn't Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-34jh-p97f-mpxf",
  "modified" : "2025-11-04T16:50:51Z",
  "published" : "2024-06-17T21:37:20Z",
  "aliases" : [ "CVE-2024-37891" ],
  "summary" : "urllib3's Proxy-Authorization request header isn't stripped during cross-origin redirects",
  "details" : "When using urllib3's proxy support with `ProxyManager`, the `Proxy-Authorization` header is only sent to the configured proxy, as expected.\n\nHowever, when sending HTTP requests *without* using urllib3's proxy support, it's possible to accidentally configure the `Proxy-Authorization` header even though it won't have any effect as the request is not using a forwarding proxy or a tunneling proxy. In those cases, urllib3 doesn't treat the `Proxy-Authorization` HTTP header as one carrying authentication material and thus doesn't strip the header on cross-origin redirects.\n\nBecause this is a highly unlikely scenario, we believe the severity of this vulnerability is low for almost all users. Out of an abundance of caution urllib3 will automatically strip the `Proxy-Authorization` header during cross-origin redirects to avoid the small chance that users are doing this on accident.\n\nUsers should use urllib3's proxy support or disable automatic redirects to achieve safe processing of the `Proxy-Authorization` header, but we still decided to strip the header by default in order to further protect users who aren't using the correct approach.\n\n## Affected usages\n\nWe believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited:\n\n* Setting the `Proxy-Authorization` header without using urllib3's built-in proxy support.\n* Not disabling HTTP redirects.\n* Either not using an HTTPS origin server or for the proxy or target origin to redirect to a malicious origin.\n\n## Remediation\n\n* Using the `Proxy-Authorization` header with urllib3's `ProxyManager`.\n* Disabling HTTP redirects using `redirects=False` when sending requests.\n* Not using the `Proxy-Authorization` header.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "urllib3"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.26.19"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "urllib3"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.0.0"
      }, {
        "fixed" : "2.2.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/urllib3/urllib3/security/advisories/GHSA-34jh-p97f-mpxf"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2024-37891"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/urllib3/urllib3/commit/40b6d1605814dd1db0a46e202d6e56f2e4c9a468"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/urllib3/urllib3/commit/accff72ecc2f6cf5a76d9570198a93ac7c90270e"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/urllib3/urllib3"
  }, {
    "type" : "WEB",
    "url" : "https://lists.debian.org/debian-lts-announce/2024/12/msg00020.html"
  }, {
    "type" : "WEB",
    "url" : "https://security.netapp.com/advisory/ntap-20240822-0003"
  }, {
    "type" : "WEB",
    "url" : "https://www.vicarius.io/vsociety/posts/proxy-authorization-header-handling-vulnerability-in-urllib3-cve-2024-37891"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-669" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-06-17T21:37:20Z",
    "nvd_published_at" : "2024-06-17T20:15:13Z"
  }
}