CVE-2026-44431: urllib3 Sensitive Headers Forwarded Across Origins Vulnerability

HIGH
Advisory Identifier: GHSA-qccp-gfcp-xxvc
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CVSS 5.3
CWE-200
Published
Advisory Summary

CVE-2026-44431 is a HIGH (CVSS 5.3) sensitive headers forwarded across origins vulnerability (CWE-200: Exposure of Sensitive Information to an Unauthorized Actor) affecting urllib3 libraries in the PyPI ecosystem. The issue involves sensitive headers forwarded across origins in proxied low-level redirects. Remediation is available by upgrading affected packages to version 2.7.0.

CVE-2026-44431 at a Glance

CVE Identifier CVE-2026-44431
GHSA Identifier GHSA-qccp-gfcp-xxvc
Severity HIGH
CVSS v3.1 Base Score 5.3
CWE Classification CWE-200: Exposure of Sensitive Information to an Unauthorized Actor
Affected Product urllib3
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 5.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2026-44431

To remediate this vulnerability, upgrade all affected urllib3 dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

urllib3 fixed: 2.7.0 
pip install urllib3>=2.7.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show urllib3

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-44431, inspect your installed packages using pip:

pip show urllib3

Analyze the terminal output to locate any version of urllib3 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.7.0), your application is affected.

Note: The pip show urllib3 command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-200: Exposure of Sensitive Information to an Unauthorized Actor, where the product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. In urllib3, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact When following cross-origin redirects for requests made using urllib3’s high-level APIs, such as `urllib3.request()`, `PoolManager.request()`, and `ProxyManager.request()`, sensitive headers — `Authorization`, `Cookie`, and `Proxy-Authorization` (defined in `Retry.DEFAULT_REMOVE_HEADERS_ON_REDIRECT`) — are stripped by default, as expected. However, cross-origin redirects followed from the low-level API via `ProxyManager.connection_from_url().urlopen(..., assert_same_host=False)` still forward these sensitive headers. ### Affected usage Applications and libraries using urllib3 versions earlier than 2.7.0 may be affected if they allow cross-origin redirects while making requests through `HTTPConnection.urlopen()` instances created via `ProxyManager.connection_from_url()`. ### Remediation Upgrade to urllib3 version 2.7.0 or later, in which sensitive headers are stripped from redirects followed by `HTTPConnection`. If upgrading is not immediately possible, avoid using this low-level redirect flow for cross-origin redirects. If appropriate for your use case, switch to `ProxyManager.request()`.

CVE-2026-44431 Affected urllib3 Versions

1 component(s)
Fixed Versions:
2.7.0
Product / Package Ecosystem Affected Versions Fixed Version
urllib3
pypi/urllib3
PyPI
≥ 1.23
< 2.7.0
2.7.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/urllib3/urllib3/security/advisories/GHSA-qccp-gfcp-xxvc
NVD — CVE-2026-44431 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-44431
urllib3 Source Repository REPOSITORY
https://github.com/urllib3/urllib3

Frequently Asked Questions

What is CVE-2026-44431?
CVE-2026-44431 is a security vulnerability in urllib3 involving Sensitive headers forwarded across origins in proxied low-level redirects under CWE-200: Exposure of Sensitive Information to an Unauthorized Actor.
Which urllib3 versions are affected?
Affected versions include releases prior to 2.7.0 across affected packages: urllib3.
What version fixes CVE-2026-44431?
Upgrading to 2.7.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is urllib3 affected?
Yes, urllib3 is affected in releases prior to 2.7.0. Upgrade your dependency to 2.7.0 or later.
What is the CVSS score of CVE-2026-44431?
CVE-2026-44431 has a CVSS v3.1 base score of 5.3 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.
What CWE is associated with CVE-2026-44431?
CVE-2026-44431 is classified under CWE-200: Exposure of Sensitive Information to an Unauthorized Actor (The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.).
How can I check PyPI dependencies for CVE-2026-44431?
Run the dependency tree command: 'pip show urllib3'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-qccp-gfcp-xxvc",
  "modified" : "2026-05-14T20:35:49Z",
  "published" : "2026-05-11T14:51:20Z",
  "aliases" : [ "CVE-2026-44431" ],
  "summary" : "urllib3: Sensitive headers forwarded across origins in proxied low-level redirects",
  "details" : "### Impact\n\nWhen following cross-origin redirects for requests made using urllib3’s high-level APIs, such as `urllib3.request()`, `PoolManager.request()`, and `ProxyManager.request()`, sensitive headers — `Authorization`, `Cookie`, and `Proxy-Authorization` (defined in `Retry.DEFAULT_REMOVE_HEADERS_ON_REDIRECT`) — are stripped by default, as expected.\n\nHowever, cross-origin redirects followed from the low-level API via `ProxyManager.connection_from_url().urlopen(..., assert_same_host=False)` still forward these sensitive headers.\n\n### Affected usage\n\nApplications and libraries using urllib3 versions earlier than 2.7.0 may be affected if they allow cross-origin redirects while making requests through `HTTPConnection.urlopen()` instances created via `ProxyManager.connection_from_url()`.\n\n### Remediation\n\nUpgrade to urllib3 version 2.7.0 or later, in which sensitive headers are stripped from redirects followed by `HTTPConnection`.\n\nIf upgrading is not immediately possible, avoid using this low-level redirect flow for cross-origin redirects. If appropriate for your use case, switch to `ProxyManager.request()`.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "urllib3"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.23"
      }, {
        "fixed" : "2.7.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/urllib3/urllib3/security/advisories/GHSA-qccp-gfcp-xxvc"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-44431"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/urllib3/urllib3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-200" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-11T14:51:20Z",
    "nvd_published_at" : "2026-05-13T16:16:57Z"
  }
}