urllib3 Add support for TLS 1.3 for pyOpenSSL when

The Fix

pip install urllib3==1.25

Based on closed urllib3/urllib3 issue #1500 · 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

@@ -22,6 +22,14 @@ dev (master)
   ``urllib3[brotli]`` extra. (Pull #1532)
 
+* Add TLSv1.3 support to CPython, pyOpenSSL, and SecureTransport ``SSLContext``
+  implementations. (Pull #1496)
+

fix.md

Option A — Upgrade to fixed release\npip install urllib3==1.25\nWhen NOT to use: This fix should not be used if the application does not support TLS 1.3.\n\n

Why This Fix Works in Production

Trigger: Add support for TLS 1.3 for pyOpenSSL when cryptography 2.5 is released
Mechanism: Adds support for TLS 1.3 to all HTTPSConnection implementations, enabling users to utilize TLS 1.3 when using pyOpenSSL with cryptography 2.5 or higher.
Why the fix works: Adds support for TLS 1.3 to all HTTPSConnection implementations, enabling users to utilize TLS 1.3 when using pyOpenSSL with cryptography 2.5 or higher. (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

Production symptom (often without a traceback): Add support for TLS 1.3 for pyOpenSSL when cryptography 2.5 is released

Proof / Evidence

GitHub issue: #1500
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: 0.67

Discussion

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

Jump to Sources Open on GitHub

“Hey friends. Has this landed yet? Anything we can do to help?”

@jMyles · 2019-02-25 · source

“Upstream requests tests are failing, I haven't had the time to setup a requests environment lately. If you'd like to do some debugging of that…”

@sethmlarson · 2019-02-25 · source

Failure Signature (Search String)

Add support for TLS 1.3 for pyOpenSSL when cryptography 2.5 is released
Upstream requests tests are failing, I haven't had the time to setup a requests environment lately. If you'd like to do some debugging of that or the best way to setup an OpenSSL

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Add support for TLS 1.3  for pyOpenSSL when cryptography 2.5 is released
Upstream requests tests are failing, I haven't had the time to setup a requests environment lately. If you'd like to do some debugging of that or the best way to setup an OpenSSL 1.1.1 env on Travis it'd be appreciated. See #1496

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Add support for TLS 1.3  for pyOpenSSL when cryptography 2.5 is released
Upstream requests tests are failing, I haven't had the time to setup a requests environment lately. If you'd like to do some debugging of that or the best way to setup an OpenSSL 1.1.1 env on Travis it'd be appreciated. See #1496

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 used if the application does not support TLS 1.3.

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 the application does not support TLS 1.3.

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 Add support for TLS 1.3 for pyOpenSSL when cryptography 2.5 is released (Fix)