Requests parsing of proxy url broken with requests 2.27.0

The Fix

pip install requests==2.27.0

Based on closed psf/requests issue #6030 · 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.

Jump to Verify Open PR/Commit

@@ -21,6 +21,7 @@
 from collections import OrderedDict
 from urllib3.util import make_headers
+from urllib3.util import parse_url
 
 from .__version__ import __version__

repro.py

{
  "chardet": {
    "version": null
  },
  "charset_normalizer": {
    "version": "2.0.9"
  },
  "cryptography": {
    "version": "36.0.1"
  },
  "idna": {
    "version": "3.3"
  },
  "implementation": {
    "name": "CPython",
    "version": "3.9.9"
  },
  "platform": {
    "release": "5.14.21-2-MANJARO",
    "system": "Linux"
  },
  "pyOpenSSL": {
    "openssl_version": "101010df",
    "version": "21.0.0"
  },
  "requests": {
    "version": "2.27.0"
  },
  "system_ssl": {
    "version": "101010df"
  },
  "urllib3": {
    "version": "1.26.7"
  },
  "using_charset_normalizer": true,
  "using_pyopenssl": true
}

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\npip install requests==2.27.0\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: parsing of proxy url broken with requests 2.27.0
Mechanism: Fixes the proxy URL parsing issue introduced in version 2.27.0 by changing the parsing method used in the `prepend_scheme_if_needed` function.
Why the fix works: Fixes the proxy URL parsing issue introduced in version 2.27.0 by changing the parsing method used in the `prepend_scheme_if_needed` function. (first fixed release: 2.27.0).

Production impact:

If left unfixed, retries/timeouts can trigger duplicate external side-effects (double charges, duplicate emails, repeated writes).

Why This Breaks in Prod

Production symptom (often without a traceback): parsing of proxy url broken with requests 2.27.0

Proof / Evidence

GitHub issue: #6030
Fix PR: https://github.com/psf/requests/pull/5917
First fixed release: 2.27.0
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.95
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.51

Discussion

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

Jump to Sources Open on GitHub

“Hi, @anneFly. Thanks for the report! This is actually a duplicate of #6027 which has been patched in #6028 and will be released sometime today.…”

@nateprewitt · 2022-01-05 · confirmation · source

Failure Signature (Search String)

parsing of proxy url broken with requests 2.27.0
It seems like this change https://github.com/psf/requests/pull/5917 unfortunately broke production for us.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
parsing of proxy url broken with requests 2.27.0
It seems like this change https://github.com/psf/requests/pull/5917 unfortunately broke production for us.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
parsing of proxy url broken with requests 2.27.0
It seems like this change https://github.com/psf/requests/pull/5917 unfortunately broke production for us.

Minimal Reproduction

repro.py

{
  "chardet": {
    "version": null
  },
  "charset_normalizer": {
    "version": "2.0.9"
  },
  "cryptography": {
    "version": "36.0.1"
  },
  "idna": {
    "version": "3.3"
  },
  "implementation": {
    "name": "CPython",
    "version": "3.9.9"
  },
  "platform": {
    "release": "5.14.21-2-MANJARO",
    "system": "Linux"
  },
  "pyOpenSSL": {
    "openssl_version": "101010df",
    "version": "21.0.0"
  },
  "requests": {
    "version": "2.27.0"
  },
  "system_ssl": {
    "version": "101010df"
  },
  "urllib3": {
    "version": "1.26.7"
  },
  "using_charset_normalizer": true,
  "using_pyopenssl": true
}

What Broke

This change caused ProxyError due to incorrect URL parsing, leading to connection failures.

Fix Options (Details)

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

pip install requests==2.27.0

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/psf/requests/pull/5917

First fixed release: 2.27.0

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.

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

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
2.27.0	Fixed

Related Issues

No related fixes found.

Cluster: requests:duplicate-processing Requests hub Requests 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.

Requests parsing of proxy url broken with requests 2.27.0 (Fix)