uvicorn forwarded-allow-ips '*' broken in combination with

The Fix

Upgrade to version 0.31.1 or later.

Based on closed Kludex/uvicorn issue #2477 · 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

@@ -56,6 +56,7 @@ def make_httpx_client(
 _TRUSTED_NOTHING: list[str] = []
 _TRUSTED_EVERYTHING = "*"
+_TRUSTED_EVERYTHING_LIST = ["*"]
 _TRUSTED_IPv4_ADDRESSES = "127.0.0.1, 10.0.0.1"
 _TRUSTED_IPv4_NETWORKS = ["127.0.0.0/8", "10.0.0.0/8"]

fix.md

Option A — Upgrade to fixed release\nUpgrade to version 0.31.1 or later.\nWhen NOT to use: Do not use this fix if you require strict host validation for security.\n\n

Why This Fix Works in Production

Trigger: --forwarded-allow-ips '*' broken in combination with gunicorn
Mechanism: The check for wildcard in trusted hosts changed from 'in' to '==' causing misbehavior
Why the fix works: Adds support for `[*]` in trusted hosts, fixing the parsing for always trust case when using `--forwarded-allow-ips` with gunicorn and uvicorn. (first fixed release: 0.31.1).

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 check for wildcard in trusted hosts changed from 'in' to '==' causing misbehavior
Production symptom (often without a traceback): --forwarded-allow-ips '*' broken in combination with gunicorn

Proof / Evidence

GitHub issue: #2477
Fix PR: https://github.com/encode/uvicorn/pull/2480
First fixed release: 0.31.1
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.75
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.80

Discussion

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

Jump to Sources Open on GitHub

“- Closed on https://github.com/encode/uvicorn/pull/2480”

@Kludex · 2024-10-09 · source

“Turns out gunicorn is parsing forwarded_allow_ips command line option and then putting its values into a list before handing it over to uvicorn's worker as…”

@theyashl · 2024-10-01 · source

Failure Signature (Search String)

--forwarded-allow-ips '*' broken in combination with gunicorn

Copy-friendly signature

signature.txt

Failure Signature
-----------------
--forwarded-allow-ips '*' broken in combination with gunicorn

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
--forwarded-allow-ips '*' broken in combination with gunicorn

What Broke

Requests with --forwarded-allow-ips '*' fail to be trusted, leading to access issues.

Why It Broke

The check for wildcard in trusted hosts changed from 'in' to '==' causing misbehavior

Fix Options (Details)

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

Upgrade to version 0.31.1 or later.

When NOT to use: Do not use this fix if you require strict host validation for security.

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

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/encode/uvicorn/pull/2480

First fixed release: 0.31.1

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

When NOT to Use This Fix

Do not use this fix if you require strict host validation for security.
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

Capture the exact failing error string in logs and tests so you can reproduce via a minimal script.
Pin production dependencies and upgrade only with a reproducible test that hits the failing path.

Version Compatibility Table

Version	Status
0.31.1	Fixed

Related Issues

No related fixes found.

Cluster: uvicorn:configuration-error All hubs All clusters

Related clusters: Data consistency Race condition SSL handshake

Sources

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

uvicorn forwarded-allow-ips '*' broken in combination with gunicorn (Fix)