urllib3 Vendor ssl.match_hostname to avoid Python 3.10

The Fix

pip install urllib3==1.26.5

Based on closed urllib3/urllib3 issue #2439 · 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

@@ -14,14 +14,12 @@
     "src/urllib3/fields.py",
     "src/urllib3/filepost.py",
-    "src/urllib3/packages/__init__.py",
-    "src/urllib3/packages/ssl_match_hostname/__init__.py",
-    "src/urllib3/packages/ssl_match_hostname/_implementation.py",

fix.md

Option A — Upgrade to fixed release\npip install urllib3==1.26.5\nWhen NOT to use: Do not use if it changes public behavior or if the failure cannot be reproduced.\n\n

Why This Fix Works in Production

Trigger: Vendor ssl.match_hostname to avoid Python 3.10 deprecation warning
Mechanism: Vendor ssl.match_hostname to avoid Python 3.10 deprecation warning.
Why the fix works: Vendor ssl.match_hostname to avoid Python 3.10 deprecation warning. (first fixed release: 1.26.5).

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

Shows up under Python 3.10 in real deployments (not just unit tests).
Production symptom (often without a traceback): Vendor ssl.match_hostname to avoid Python 3.10 deprecation warning

Proof / Evidence

GitHub issue: #2439
Fix PR: https://github.com/urllib3/urllib3/pull/2198
First fixed release: 1.26.5
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.65

Discussion

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

Jump to Sources Open on GitHub

“@chetanugale @Pradhvan Because there's some time sensitivity to this PR I'd recommend both of you work on this and whoever has a PR that's ready…”

@sethmlarson · 2021-10-07 · confirmation · source

“Fixed in https://github.com/urllib3/urllib3/pull/2448”

@sethmlarson · 2021-10-08 · confirmation · source

“Thanks! I would've sent a PR but it was a bit tricky to figure out how to attack it with no prior knowledge of the…”

@AdamWill · 2021-10-01 · source

“@chetanugale are you still working on this ? If not, I am free now. I can pick this up now if you're busy. 😄”

@Pradhvan · 2021-10-07 · source

Failure Signature (Search String)

Vendor ssl.match_hostname to avoid Python 3.10 deprecation warning
As reported by @AdamWill in https://github.com/urllib3/urllib3/issues/2200#issuecomment-931759912, we're issuing deprecation warnings for using `ssl.match_hostname()` on Python

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Vendor ssl.match_hostname to avoid Python 3.10 deprecation warning
As reported by @AdamWill in https://github.com/urllib3/urllib3/issues/2200#issuecomment-931759912, we're issuing deprecation warnings for using `ssl.match_hostname()` on Python 3.10:

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Vendor ssl.match_hostname to avoid Python 3.10 deprecation warning
As reported by @AdamWill in https://github.com/urllib3/urllib3/issues/2200#issuecomment-931759912, we're issuing deprecation warnings for using `ssl.match_hostname()` on Python 3.10:

Environment

Python: 3.10

Fix Options (Details)

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

pip install urllib3==1.26.5

When NOT to use: Do not use if it changes public behavior or if the failure cannot be reproduced.

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/2198

First fixed release: 1.26.5

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

When NOT to Use This Fix

Do not use if it changes public behavior or if the failure cannot be reproduced.

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
1.26.5	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 Vendor ssl.match_hostname to avoid Python 3.10 deprecation warning (Fix)