urllib3 Requesting release of 1.26.15 (Fix)

The Fix

pip install urllib3==1.26.15

Based on closed urllib3/urllib3 issue #2929 · PR/commit linked

Production note: This usually shows up under retries/timeouts. Treat it as a side-effect risk until you can verify behavior with a canary + real traffic.

Open PR/Commit

@@ -1,6 +1,14 @@
 =======
 
+1.26.15 (2023-03-10)
+--------------------
+

fix.md

Option A — Upgrade to fixed release\npip install urllib3==1.26.15\nWhen NOT to use: This fix should not be used if the application relies on the previous timeout behavior.\n\nOption C — Workaround\nwe currently have for our issue is to increase all timeouts, but that causes other issues for our software.\nWhen NOT to use: This fix should not be used if the application relies on the previous timeout behavior.\n\n

Why This Fix Works in Production

Trigger: The workaround we currently have for our issue is to increase all timeouts, but that causes other issues for our software.
Mechanism: Releases version 1.26.15 of urllib3, addressing several issues including socket timeout values and IDNA handling.
Why the fix works: Releases version 1.26.15 of urllib3, addressing several issues including socket timeout values and IDNA handling. (first fixed release: 1.26.15).

Production impact:

If left unfixed, tail latency can spike under load and surface as timeouts/retries (amplifying incident impact).

Why This Breaks in Prod

Production symptom (often without a traceback): The workaround we currently have for our issue is to increase all timeouts, but that causes other issues for our software.

Proof / Evidence

GitHub issue: #2929
Fix PR: https://github.com/urllib3/urllib3/pull/2931
First fixed release: 1.26.15
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.75
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.87

Discussion

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

Jump to Sources Open on GitHub

“That sounds like a good idea, we actually allow anyone to kick off a release-candidate PR”

@sethmlarson · 2023-03-08 · source

“Done! https://github.com/urllib3/urllib3/pull/2931”

@sethmlarson · 2023-03-11 · source

Failure Signature (Search String)

The workaround we currently have for our issue is to increase all timeouts, but that causes other issues for our software.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
The workaround we currently have for our issue is to increase all timeouts, but that causes other issues for our software.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
The workaround we currently have for our issue is to increase all timeouts, but that causes other issues for our software.

Environment

urllib3: 1.26.14

What Broke

Increased timeouts caused other issues in the software, impacting performance.

Fix Options (Details)

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

pip install urllib3==1.26.15

When NOT to use: This fix should not be used if the application relies on the previous timeout behavior.

Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.

Option C — Workaround Temporary workaround

we currently have for our issue is to increase all timeouts, but that causes other issues for our software.

When NOT to use: This fix should not be used if the application relies on the previous timeout behavior.

Use only if you cannot change versions today. Treat this as a stopgap and remove once upgraded.

Option D — Guard side-effects with OnceOnly Guardrail for side-effects

Mitigate duplicate external side-effects under retries/timeouts/agent loops by gating the operation before calling external systems.

Place OnceOnly between your code/agent and real side-effects (Stripe, emails, CRM, APIs).
Use a stable key per side-effect (e.g., customer_id + action + idempotency_key).
Fail-safe: configure fail-open vs fail-closed based on blast radius and spend risk.

Show example snippet (optional)

onceonly.py

from onceonly import OnceOnly
import os

once = OnceOnly(api_key=os.environ["ONCEONLY_API_KEY"], fail_open=True)

# Stable idempotency key per real side-effect.
# Use a request id / job id / webhook delivery id / Stripe event id, etc.
event_id = "evt_..."  # replace
key = f"stripe:webhook:{event_id}"

res = once.check_lock(key=key, ttl=3600)
if res.duplicate:
    return {"status": "already_processed"}

# Safe to execute the side-effect exactly once.
handle_event(event_id)

See OnceOnly SDK

When NOT to use: Do not use this to hide logic bugs or data corruption. Use it to block duplicate external side-effects and enforce tool permissions/spend caps.

Fix reference: https://github.com/urllib3/urllib3/pull/2931

First fixed release: 1.26.15

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

When NOT to Use This Fix

This fix should not be used if the application relies on the previous timeout behavior.
Do not use this to hide logic bugs or data corruption. Use it to block duplicate external side-effects and enforce tool permissions/spend caps.

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.
Make timeouts explicit and test them (unit + integration) to avoid silent behavior changes.
Instrument retries (attempt count + reason) and alert on spikes to catch dependency slowdowns.

Version Compatibility Table

Version	Status
1.26.15	Fixed

Related Issues

No related fixes found.

Cluster: urllib3:timeout urllib3 hub urllib3 best practices All hubs All clusters

Related clusters: Configuration error Data consistency SSL handshake

Sources

We don’t republish the full GitHub discussion text. Use the links above for context.