CVE-2018-25091: Urllib3 Authorization Header Forwarded On Redirect Vulnerability

MODERATE
Advisory Identifier: GHSA-gwvm-45gx-3cf8
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CVSS 6.1
CWE-601 CWE-200
Published
Advisory Summary

CVE-2018-25091 is a MODERATE (CVSS 6.1) authorization header forwarded on redirect vulnerability (CWE-601: URL Redirection to Untrusted Site ('Open Redirect')) affecting Urllib3 libraries in the PyPI ecosystem. The issue involves authorization header forwarded on redirect. Remediation is available by upgrading affected packages to version 1.24.2.

CVE-2018-25091 at a Glance

CVE Identifier CVE-2018-25091
GHSA Identifier GHSA-gwvm-45gx-3cf8
Severity MODERATE
CVSS v3.1 Base Score 6.1
CWE Classification CWE-601: URL Redirection to Untrusted Site ('Open Redirect')
Affected Product Urllib3
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 6.1

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:R/S:C/C:L/I:L/A:N).

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

How to Fix CVE-2018-25091

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: 1.24.2 
pip install urllib3>=1.24.2
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-2018-25091, 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 1.24.2), 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-601: URL Redirection to Untrusted Site ('Open Redirect'), where the web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect. 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

urllib3 before 1.24.2 does not remove the authorization HTTP header when following a cross-origin redirect (i.e., a redirect that differs in host, port, or scheme). This can allow for credentials in the authorization header to be exposed to unintended hosts or transmitted in cleartext. NOTE: this issue exists because of an incomplete fix for CVE-2018-20060 (which was case-sensitive).

CVE-2018-25091 Affected Urllib3 Versions

1 component(s)
Fixed Versions:
1.24.2
Product / Package Ecosystem Affected Versions Fixed Version
urllib3
pypi/urllib3
PyPI
< 1.24.2
1.24.2

References

NVD — CVE-2018-25091 NVD
https://nvd.nist.gov/vuln/detail/CVE-2018-25091
Urllib3 Source Repository REPOSITORY
https://github.com/urllib3/urllib3/issues/1510
Security Fix Commit FIX COMMIT
https://github.com/urllib3/urllib3/commit/adb358f8e06865406d1f05e581a16cbea2136fbc
Urllib3 Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/urllib3/PYSEC-2023-207.yaml
Urllib3 Source Repository REPOSITORY
https://github.com/urllib3/urllib3
Urllib3 Source Repository REPOSITORY
https://github.com/urllib3/urllib3/compare/1.24.1...1.24.2

Frequently Asked Questions

What is CVE-2018-25091?
CVE-2018-25091 is a security vulnerability in Urllib3 involving Authorization Header forwarded on redirect under CWE-601: URL Redirection to Untrusted Site ('Open Redirect').
Which Urllib3 versions are affected?
Affected versions include releases prior to 1.24.2 across affected packages: urllib3.
What version fixes CVE-2018-25091?
Upgrading to 1.24.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is urllib3 affected?
Yes, urllib3 is affected in releases prior to 1.24.2. Upgrade your dependency to 1.24.2 or later.
What is the CVSS score of CVE-2018-25091?
CVE-2018-25091 has a CVSS v3.1 base score of 6.1 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2018-25091?
CVE-2018-25091 is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect') (The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.).
How can I check PyPI dependencies for CVE-2018-25091?
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-gwvm-45gx-3cf8",
  "modified" : "2024-11-18T23:15:14Z",
  "published" : "2023-10-15T21:30:26Z",
  "aliases" : [ "CVE-2018-25091" ],
  "summary" : "Authorization Header forwarded on redirect",
  "details" : "urllib3 before 1.24.2 does not remove the authorization HTTP header when following a cross-origin redirect (i.e., a redirect that differs in host, port, or scheme). This can allow for credentials in the authorization header to be exposed to unintended hosts or transmitted in cleartext. NOTE: this issue exists because of an incomplete fix for CVE-2018-20060 (which was case-sensitive).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "urllib3"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.24.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2018-25091"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/urllib3/urllib3/issues/1510"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/urllib3/urllib3/commit/adb358f8e06865406d1f05e581a16cbea2136fbc"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/urllib3/PYSEC-2023-207.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/urllib3/urllib3"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/urllib3/urllib3/compare/1.24.1...1.24.2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-200", "CWE-601" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2023-10-17T14:21:39Z",
    "nvd_published_at" : "2023-10-15T19:15:09Z"
  }
}