urllib3 Emscripten support emits an InsecureRequestWarning

The Fix

pip install urllib3==2.2.1

Based on closed urllib3/urllib3 issue #3331 · 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

@@ -0,0 +1 @@
@@ -0,0 +1 @@
+Fixed issue where ``InsecureRequestWarning`` was emitted for HTTPS connections when using Emscripten.
diff --git a/src/urllib3/contrib/emscripten/connection.py b/src/urllib3/contrib/emscripten/connection.py
index 9090e51d18..2ceb4579eb 100644

fix.md

Option A — Upgrade to fixed release\npip install urllib3==2.2.1\nWhen NOT to use: This fix should not be used if the application requires strict verification for all connections.\n\n

Why This Fix Works in Production

Trigger: This is a side-effect of us using JavaScript APIs instead of Python TLS and setting `is_verified` on the `EmscriptenHTTPConnection` so urllib3 is emitting an
Mechanism: The EmscriptenHTTPConnection was incorrectly setting is_verified, causing warnings for HTTPS requests
Why the fix works: Fixes the issue where InsecureRequestWarning is emitted for HTTPS connections when using Emscripten by setting the proper value of is_verified. (first fixed release: 2.2.1).

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

The EmscriptenHTTPConnection was incorrectly setting is_verified, causing warnings for HTTPS requests
Production symptom (often without a traceback): This is a side-effect of us using JavaScript APIs instead of Python TLS and setting `is_verified` on the `EmscriptenHTTPConnection` so urllib3 is emitting an `InsecureRequestWarning` for every request, even ones that are using HTTPS.

Proof / Evidence

GitHub issue: #3331
Fix PR: https://github.com/urllib3/urllib3/pull/3333
First fixed release: 2.2.1
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.95
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.71

Discussion

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

Jump to Sources Open on GitHub

“This is a side-effect of us using JavaScript APIs instead of Python TLS and setting is_verified on the EmscriptenHTTPConnection so urllib3 is emitting an InsecureRequestWarning for every request, even ones that are using HTTPS. * Set the pr”

Issue thread · issue description · source

Failure Signature (Search String)

This is a side-effect of us using JavaScript APIs instead of Python TLS and setting `is_verified` on the `EmscriptenHTTPConnection` so urllib3 is emitting an
* Add a test case that asserts that an `InsecureRequestWarning` is emitted for HTTP and isn't emitted for HTTPS.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
This is a side-effect of us using JavaScript APIs instead of Python TLS and setting `is_verified` on the `EmscriptenHTTPConnection` so urllib3 is emitting an `InsecureRequestWarning` for every request, even ones that are using HTTPS.
* Add a test case that asserts that an `InsecureRequestWarning` is emitted for HTTP and isn't emitted for HTTPS.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
This is a side-effect of us using JavaScript APIs instead of Python TLS and setting `is_verified` on the `EmscriptenHTTPConnection` so urllib3 is emitting an `InsecureRequestWarning` for every request, even ones that are using HTTPS.
* Add a test case that asserts that an `InsecureRequestWarning` is emitted for HTTP and isn't emitted for HTTPS.

What Broke

InsecureRequestWarning was emitted for HTTPS requests, leading to confusion and potential security concerns.

Why It Broke

The EmscriptenHTTPConnection was incorrectly setting is_verified, causing warnings for HTTPS requests

Fix Options (Details)

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

pip install urllib3==2.2.1

When NOT to use: This fix should not be used if the application requires strict verification for all connections.

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/3333

First fixed release: 2.2.1

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

When NOT to Use This Fix

This fix should not be used if the application requires strict verification for all connections.

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
2.2.1	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 Emscripten support emits an InsecureRequestWarning even when using HTTPS (Fix)