uvicorn Catch `HttpParserInvalidMethodError` exception (Fix)

The Fix

Upgrade to version 0.11.4 or later.

Based on closed Kludex/uvicorn issue #75 · 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%.

Jump to Verify Open PR/Commit

@@ -93,6 +93,10 @@ def eof_received(self):
         try:
             self.parser.feed_data(data)
+        except httptools.parser.errors.HttpParserError:
+            msg = "Invalid HTTP request received."
+            self.logger.warn(msg)

repro.py

uvicorn[7423]: Unhandled exception in event loop
uvicorn[7423]: Traceback (most recent call last):
uvicorn[7423]:   File "uvloop/handles/stream.pyx", line 784, in uvloop.loop.__uv_stream_on_read_impl
uvicorn[7423]:   File "uvloop/handles/stream.pyx", line 563, in uvloop.loop.UVStream._on_read
uvicorn[7423]:   File "/home/web/.virtualenvs/mesh/lib/python3.5/site-packages/uvicorn/protocols/http.py", line 212, in data_received
uvicorn[7423]:     self.request_parser.feed_data(data)
uvicorn[7423]:   File "httptools/parser/parser.pyx", line 193, in httptools.parser.parser.HttpParser.feed_data
uvicorn[7423]: httptools.parser.errors.HttpParserInvalidMethodError: invalid HTTP method

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

fix.md

Option A — Upgrade to fixed release\nUpgrade to version 0.11.4 or later.\nWhen NOT to use: This fix should not be used if the underlying issue of invalid HTTP methods is not addressed.\n\n

Why This Fix Works in Production

Trigger: Catch `HttpParserInvalidMethodError` exception
Mechanism: The HTTP parser was not handling invalid HTTP methods, leading to unhandled exceptions
Why the fix works: Catch `HttpParserInvalidMethodError` exception in the HTTP protocol handling to prevent unhandled exceptions. (first fixed release: 0.11.4).

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 3.5 in real deployments (not just unit tests).
The HTTP parser was not handling invalid HTTP methods, leading to unhandled exceptions
Surfaces as: Catch `HttpParserInvalidMethodError` exception

Proof / Evidence

GitHub issue: #75
Fix PR: https://github.com/kludex/uvicorn/pull/110
First fixed release: 0.11.4
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.54

Discussion

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

Jump to Sources Open on GitHub

“@ChillarAnand you use method is not in parser , but uvicorn should catch this error.”

@zeromake · 2018-06-01 · source

“These errors are showing up in production. I am not sure why that is happening. I couldn't reproduce it locally.”

@ChillarAnand · 2018-06-01 · source

“@ChillarAnand The exception could be explicitly handled, but the underlying issue is what @zeromake said. If you could debug the information associated with the request…”

@jordaneremieff · 2018-06-01 · source

“I will log the data and see what is happening. Thanks @erm @zeromake”

@ChillarAnand · 2018-06-01 · source

Failure Signature (Search String)

Catch `HttpParserInvalidMethodError` exception

Error Message

Stack trace

error.txt

Error Message
-------------
Catch `HttpParserInvalidMethodError` exception

Minimal Reproduction

repro.py

uvicorn[7423]: Unhandled exception in event loop
uvicorn[7423]: Traceback (most recent call last):
uvicorn[7423]:   File "uvloop/handles/stream.pyx", line 784, in uvloop.loop.__uv_stream_on_read_impl
uvicorn[7423]:   File "uvloop/handles/stream.pyx", line 563, in uvloop.loop.UVStream._on_read
uvicorn[7423]:   File "/home/web/.virtualenvs/mesh/lib/python3.5/site-packages/uvicorn/protocols/http.py", line 212, in data_received
uvicorn[7423]:     self.request_parser.feed_data(data)
uvicorn[7423]:   File "httptools/parser/parser.pyx", line 193, in httptools.parser.parser.HttpParser.feed_data
uvicorn[7423]: httptools.parser.errors.HttpParserInvalidMethodError: invalid HTTP method

Environment

Python: 3.5

What Broke

Production errors occurred due to unhandled exceptions from invalid HTTP methods.

Why It Broke

The HTTP parser was not handling invalid HTTP methods, leading to unhandled exceptions

Fix Options (Details)

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

Upgrade to version 0.11.4 or later.

When NOT to use: This fix should not be used if the underlying issue of invalid HTTP methods is not addressed.

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

Fix reference: https://github.com/kludex/uvicorn/pull/110

First fixed release: 0.11.4

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

When NOT to Use This Fix

This fix should not be used if the underlying issue of invalid HTTP methods is not addressed.

Verify Fix

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

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
0.11.4	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.