urllib3 Shouldn't urllib3 verify SSL/TLS certificates by

The Fix

pip install urllib3==1.25

Based on closed urllib3/urllib3 issue #1454 · PR/commit linked

Production note: Most teams hit this during upgrades or environment changes. Roll out with a canary and smoke critical endpoints (health, OpenAPI/docs) before 100%.

Open PR/Commit

@@ -16,6 +16,8 @@ dev (master)
   given and no password was given. Instead an ``SSLError`` is raised. (Pull #1489)
 
+* Require and validate certificates by default when using HTTPS (Pull #1507)
+
 * ... [Short description of non-trivial change.] (Issue #)

fix.md

Option A — Upgrade to fixed release\npip install urllib3==1.25\nWhen NOT to use: This fix should not be applied if backward compatibility with existing code is a priority.\n\n

Why This Fix Works in Production

Trigger: Shouldn't urllib3 verify SSL/TLS certificates by default ?
Mechanism: The default behavior of urllib3 did not require SSL/TLS certificate validation for HTTPS requests
Why the fix works: Changes the default behavior of urllib3 to require and validate SSL/TLS certificates for HTTPS requests. (first fixed release: 1.25).

Production impact:

If left unfixed, the same config can fail only in production (env differences), causing startup failures or partial feature outages.

Why This Breaks in Prod

The default behavior of urllib3 did not require SSL/TLS certificate validation for HTTPS requests
Production symptom (often without a traceback): Shouldn't urllib3 verify SSL/TLS certificates by default ?

Proof / Evidence

GitHub issue: #1454
Fix PR: https://github.com/urllib3/urllib3/pull/1507
First fixed release: 1.25
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.95
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.75

Discussion

High-signal excerpts from the issue thread (symptoms, repros, edge-cases).

Jump to Sources Open on GitHub

“I'd say this is probably ready to go then :)”

@sethmlarson · 2018-10-16 · source

“I think if we were to "do-it-all-over" we'd have TLS verification on by default but to preserve backwards compatibility we'll probably keep the current behavior…”

@sethmlarson · 2018-10-16 · source

“For the records, see https://github.com/SeleniumHQ/selenium/issues/6534 for a case where switching from httplib to urllib3 accidentally disabled certificate validation ( the change introducing the issue https://github.com/SeleniumHQ/selenium/commit/8d98f3223c3”

@jerome-nexedi · 2018-10-16 · source

“I would personally be totally okay with us changing this behavior in a minor release (Python did it in a patch release, hilariously). I would…”

@theacodes · 2018-10-16 · source

Failure Signature (Search String)

Shouldn't urllib3 verify SSL/TLS certificates by default ?
... urllib3 brings many critical features that are missing from the Python standard libraries:

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Shouldn't urllib3 verify SSL/TLS certificates by default ?
... urllib3 brings many critical features that are missing from the Python standard libraries:

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Shouldn't urllib3 verify SSL/TLS certificates by default ?
... urllib3 brings many critical features that are missing from the Python standard libraries:

What Broke

Users migrating from urllib2 or httplib may experience disabled certificate validation, leading to security vulnerabilities.

Why It Broke

The default behavior of urllib3 did not require SSL/TLS certificate validation for HTTPS requests

Fix Options (Details)

Option A — Upgrade to fixed release Safe default (recommended)

pip install urllib3==1.25

When NOT to use: This fix should not be applied if backward compatibility with existing code is a priority.

Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.

Fix reference: https://github.com/urllib3/urllib3/pull/1507

First fixed release: 1.25

Last verified: 2026-02-09. Validate in your environment.

When NOT to Use This Fix

This fix should not be applied if backward compatibility with existing code is a priority.

Did This Fix Work in Your Case?

Quick signal helps us prioritize which fixes to verify and improve.

Prevention

Add a CI check that diffs key outputs after upgrades (OpenAPI schema snapshots, JSON payload shapes, CLI output).
Upgrade behind a canary and run integration tests against the canary before 100% rollout.
Add a TLS smoke test that performs a real handshake in CI (include CA bundle validation and hostname checks).
Alert on handshake failures by error string and endpoint to catch cert/CA changes quickly.

Version Compatibility Table

Version	Status
1.25	Fixed

Related Issues

No related fixes found.

Cluster: urllib3:configuration-error urllib3 hub urllib3 best practices All hubs All clusters

Related clusters: Data consistency SSL handshake Other

Sources

We don’t republish the full GitHub discussion text. Use the links above for context.

urllib3 Shouldn't urllib3 verify SSL/TLS certificates by default ? (Fix)