The Fix
pip install urllib3==1.25
Based on closed urllib3/urllib3 issue #1368 · 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 is not applicable if the licensing information is already present.\n\n
Why This Fix Works in Production
- Trigger: Missing License text on securetransport.py
- Mechanism: Added licensing information to securetransport.py, acknowledging the oscrypto library.
- Why the fix works: Added licensing information to securetransport.py, acknowledging the oscrypto library. (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
- Production symptom (often without a traceback): Missing License text on securetransport.py
Proof / Evidence
- GitHub issue: #1368
- 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: 0.75
Discussion
High-signal excerpts from the issue thread (symptoms, repros, edge-cases).
“HI @wbond, feel free to send a PR to include the exact text you want to be displayed. Thankfully, both projects are MIT-licensed.”
“It looks like Lukasa put the licensing info in urllib3/contrib/_securetransport/bindings.py in #1122.”
“Well, my point is that not just bindings.py is derived, securetransport.py appears to be derived too, so either a LICENSE file listing which files are…”
“Putting licensing information into urllib3/contrib/securetransport.py sounds reasonable to me. cc: @Lukasa”
Failure Signature (Search String)
- Missing License text on securetransport.py
- - https://github.com/wbond/oscrypto/blob/master/oscrypto/_osx/tls.py#L90
Copy-friendly signature
Failure Signature
-----------------
Missing License text on securetransport.py
- https://github.com/wbond/oscrypto/blob/master/oscrypto/_osx/tls.py#L90
Error Message
Signature-only (no traceback captured)
Error Message
-------------
Missing License text on securetransport.py
- https://github.com/wbond/oscrypto/blob/master/oscrypto/_osx/tls.py#L90
What Broke
Lack of licensing information could lead to legal issues regarding code usage.
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 is not applicable if the licensing information is already present.
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.