urllib3 allow http requests through https proxy (Fix)

The Fix

pip install urllib3==1.25.9

Based on closed urllib3/urllib3 issue #476 · 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

@@ -282,6 +282,9 @@ In chronological order:
     HTTPConnectionPool._make_request(), also for BaseExceptions.
 
+* Jorge Lopez Silva <https://github.com/jalopezsilva>
+  * Added support for forwarding requests through HTTPS proxies.
+

fix.md

Option A — Upgrade to fixed release\npip install urllib3==1.25.9\nWhen NOT to use: Do not use this fix if you require HTTPS requests to be tunneled through HTTPS proxies.\n\n

Why This Fix Works in Production

Trigger: - http://wiki.squid-cache.org/Features/HTTPS#Direct_SSL.2BAC8-TLS_connection
Mechanism: The ProxyManager was unnecessarily tunneling HTTP requests through HTTPS proxies
Why the fix works: Adds support for forwarding requests through HTTPS proxies, allowing HTTP requests to be sent through an HTTPS proxy without unnecessary tunneling. (first fixed release: 1.25.9).

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 ProxyManager was unnecessarily tunneling HTTP requests through HTTPS proxies
Production symptom (often without a traceback): - http://wiki.squid-cache.org/Features/HTTPS#Direct_SSL.2BAC8-TLS_connection

Proof / Evidence

GitHub issue: #476
Fix PR: https://github.com/urllib3/urllib3/pull/1679
First fixed release: 1.25.9
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.74

Discussion

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

Jump to Sources Open on GitHub

“Support for this has landed in master in https://github.com/urllib3/urllib3/pull/1679”

@sethmlarson · 2020-08-29 · confirmation · source

Failure Signature (Search String)

- http://wiki.squid-cache.org/Features/HTTPS#Direct_SSL.2BAC8-TLS_connection
case for me is: send http req --ssl--> https proxy (manipulates and fwds) --> origin. but `ProxyManager` tunnels these reqs unnecessarily (?).

Copy-friendly signature

signature.txt

Failure Signature
-----------------
- http://wiki.squid-cache.org/Features/HTTPS#Direct_SSL.2BAC8-TLS_connection
case for me is: send http req --ssl--> https proxy (manipulates and fwds) --> origin. but `ProxyManager` tunnels these reqs unnecessarily (?).

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
- http://wiki.squid-cache.org/Features/HTTPS#Direct_SSL.2BAC8-TLS_connection
case for me is: send http req --ssl--> https proxy (manipulates and fwds) --> origin. but `ProxyManager` tunnels these reqs unnecessarily (?).

What Broke

HTTP requests through HTTPS proxies were not being forwarded correctly, causing failures.

Why It Broke

The ProxyManager was unnecessarily tunneling HTTP requests through HTTPS proxies

Fix Options (Details)

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

pip install urllib3==1.25.9

When NOT to use: Do not use this fix if you require HTTPS requests to be tunneled through HTTPS proxies.

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/1679

First fixed release: 1.25.9

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

When NOT to Use This Fix

Do not use this fix if you require HTTPS requests to be tunneled through HTTPS proxies.

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
1.25.9	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

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