What is CVE-2018-25091?

CVE-2018-25091 is a medium-severity vulnerability in Python Urllib3, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 6.1/10. Published 2023-10-15.

How severe is CVE-2018-25091?

Medium severity. CVSS v3 base score is 6.1 out of 10.

Open Redirect in Python Urllib3

CVE-2018-25091

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).

Vulnerability class: Open Redirect

Published 2023-10-15 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.005 (41.6th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 42nd percentile — 41.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000

Affected products

Python Urllib3

Weakness classification (CWE)

CWE-601 — URL Redirection to Untrusted Site (Open Redirect)

References

github.com/urllib3/urllib3/issues/1510 (Patch, Issue Tracking, Vendor Advisory)
github.com/urllib3/urllib3/commit/adb358f8e06865406d1f05e581a16cbea2136fbc (Patch)
github.com/urllib3/urllib3/compare/1.24.1...1.24.2 (Patch)

Frequently asked questions

What is CVE-2018-25091?: CVE-2018-25091 is a medium-severity vulnerability in Python Urllib3, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 6.1/10. Published 2023-10-15.
How severe is CVE-2018-25091?: Medium severity. CVSS v3 base score is 6.1 out of 10.