The Fix
pip install urllib3==1.25
Based on closed urllib3/urllib3 issue #884 · 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%.
@@ -1,134 +1,71 @@
@@ -1,134 +1,71 @@
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urllib3
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Option A — Upgrade to fixed release\npip install urllib3==1.25\nWhen NOT to use: Do not apply this fix if the documentation structure is already clear and comprehensive.\n\n
Why This Fix Works in Production
- Trigger: - [x] custom tls stuff
- Mechanism: The documentation was outdated and poorly organized, leading to confusion among users
- Why the fix works: Finishes up the new documentation, updating the README and adding advanced usage docs. (first fixed release: 1.25).
- 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- The documentation was outdated and poorly organized, leading to confusion among users
- Production symptom (often without a traceback): - [x] custom tls stuff
Proof / Evidence
- GitHub issue: #884
- Fix PR: https://github.com/urllib3/urllib3/pull/940
- 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: 0.92
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“Just ran into @mjpieters at the PDX airport and he had some feedback about our docs, added some ideas to the original issue. Keep em'…”
“re: the user/advanced divide: we can always move things around. I just need a starting structure so I can start writing.”
“Some final questions before I start sending PRs: 1”
“Excellent! On Wed, Jun 1, 2016, 5:48 PM Andrey Petrov [email protected] wrote: > Just ran into a stackoverflower at PDX and he had some feedback…”
Failure Signature (Search String)
- - [x] custom tls stuff
- 4. SSL verification
Copy-friendly signature
Failure Signature
-----------------
- [x] custom tls stuff
4. SSL verification
Error Message
Signature-only (no traceback captured)
Error Message
-------------
- [x] custom tls stuff
4. SSL verification
What Broke
Users experienced difficulty understanding library usage, resulting in increased support requests.
Why It Broke
The documentation was outdated and poorly organized, leading to confusion among users
Fix Options (Details)
Option A — Upgrade to fixed release Safe default (recommended)
pip install urllib3==1.25
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/940
First fixed release: 1.25
Last verified: 2026-02-09. Validate in your environment.
When NOT to Use This Fix
- Do not apply this fix if the documentation structure is already clear and comprehensive.
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.
Sources
We don’t republish the full GitHub discussion text. Use the links above for context.