The Fix
pip install urllib3==1.25
Based on closed urllib3/urllib3 issue #1451 · 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%.
@@ -22,6 +22,14 @@ dev (master)
``urllib3[brotli]`` extra. (Pull #1532)
+* Add TLSv1.3 support to CPython, pyOpenSSL, and SecureTransport ``SSLContext``
+ implementations. (Pull #1496)
+
Option A — Upgrade to fixed release\npip install urllib3==1.25\nWhen NOT to use: This fix should not be used if compatibility with older Python versions is required.\n\n
Why This Fix Works in Production
- Trigger: Remove/fix all deprecated features in the ssl module
- Mechanism: Adds support for TLS 1.3 to all HTTPSConnection implementations and drops deprecated ciphers using DSS key exchange.
- Why the fix works: Adds support for TLS 1.3 to all HTTPSConnection implementations and drops deprecated ciphers using DSS key exchange. (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
- Shows up under Python 3.6 in real deployments (not just unit tests).
- Production symptom (often without a traceback): Remove/fix all deprecated features in the ssl module
Proof / Evidence
- GitHub issue: #1451
- Fix PR: https://github.com/urllib3/urllib3/pull/1496
- 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: 0.73
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“Python 3.6.x/3.7.x deprecated a lot of features in the ssl module. We should upgrade to using the latest ones that aren't deprecated and provide a proper fallback.”
Failure Signature (Search String)
- Remove/fix all deprecated features in the ssl module
Copy-friendly signature
Failure Signature
-----------------
Remove/fix all deprecated features in the ssl module
Python 3.6.x/3.7.x deprecated a lot of features in the ssl module. We should upgrade to using the latest ones that aren't deprecated and provide a proper fallback.
Error Message
Signature-only (no traceback captured)
Error Message
-------------
Remove/fix all deprecated features in the ssl module
Python 3.6.x/3.7.x deprecated a lot of features in the ssl module. We should upgrade to using the latest ones that aren't deprecated and provide a proper fallback.
Environment
- Python: 3.6
What Broke
Users experienced issues with deprecated SSL features leading to connection failures.
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/1496
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 used if compatibility with older Python versions is required.
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.