Requests Leading slash in uri followed by column fails (Fix)

The Fix

pip install requests==2.32.0

Based on closed psf/requests issue #6643 · 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

@@ -390,6 +390,9 @@ def request_url(self, request, proxies):
 
         url = request.path_url
+        if url.startswith("//"):  # Don't confuse urllib3
+            url = f"/{url.lstrip('/')}"
+

repro.py

Traceback (most recent call last):
  File "/usr/local/lib/python3.11/site-packages/urllib3/util/url.py", line 425, in parse_url
    host, port = _HOST_PORT_RE.match(host_port).groups()  # type: ignore[union-attr]
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'groups'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.11/site-packages/requests/api.py", line 73, in get
    return request("get", url, params=params, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/requests/api.py", line 59, in request
    return session.request(method=method, url=url, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/requests/sessions.py", line 589, in request
    resp = self.send(prep, **send_kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/requests/sessions.py", line 703, in send
    r = adapter.send(request, **kwargs)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/requests/adapters.py", line 486, in send
    resp = conn.urlopen(
           ^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/urllib3/connectionpool.py", line 711, in urlopen
    parsed_url = parse_url(url)
                 ^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/urllib3/util/url.py", line 451, in parse_url
    raise LocationParseError(source_url) from e
urllib3.exceptions.LocationParseError: Failed to parse: //v:h

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==2.32.0\nWhen NOT to use: This fix is not applicable for URLs where leading slashes are intended for valid paths.\n\n

Why This Fix Works in Production

Trigger: host, port = _HOST_PORT_RE.match(host_port).groups() # type: ignore[union-attr]
Mechanism: Leading slashes in the URL path cause urllib3 to misinterpret the URL structure
Why the fix works: Trim excess leading path separators to prevent URL parsing issues in urllib3. (first fixed release: 2.32.0).

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 3.11 in real deployments (not just unit tests).
Leading slashes in the URL path cause urllib3 to misinterpret the URL structure
Surfaces as: Traceback (most recent call last):

Proof / Evidence

GitHub issue: #6643
Fix PR: https://github.com/psf/requests/pull/6644
First fixed release: 2.32.0
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.31

Discussion

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

Jump to Sources Open on GitHub

“I can reproduce this with cc @sethmlarson @pquentin”

@sigmavirus24 · 2024-02-22 · source

“Also, yes, I verified that RFC3986 allows : as a non-percent-encoded character in the path: https://datatracker.ietf.org/doc/html/rfc3986.html#section-3.3”

@sigmavirus24 · 2024-02-22 · source

“And I think the problem is the // in the path which is tripping up the parsing as // is the delimiter for what should…”

@sigmavirus24 · 2024-02-22 · source

“Also reported this up to urllib3 https://github.com/urllib3/urllib3/issues/3352”

@sigmavirus24 · 2024-02-22 · source

Failure Signature (Search String)

host, port = _HOST_PORT_RE.match(host_port).groups() # type: ignore[union-attr]

Error Message

Stack trace

error.txt

Error Message
-------------
Traceback (most recent call last):
  File "/usr/local/lib/python3.11/site-packages/urllib3/util/url.py", line 425, in parse_url
    host, port = _HOST_PORT_RE.match(host_port).groups()  # type: ignore[union-attr]
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'groups'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.11/site-packages/requests/api.py", line 73, in get
    return request("get", url, params=params, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/requests/api.py", line 59, in request
    return session.request(method=method, url=url, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/requests/sessions.py", line 589, in request
    resp = self.send(prep, **send_kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/requests/sessions.py", line 703, in send
    r = adapter.send(request, **kwargs)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/requests/adapters.py", line 486, in send
    resp = conn.urlopen(
           ^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-pac
... (truncated) ...

Minimal Reproduction

repro.py

Traceback (most recent call last):
  File "/usr/local/lib/python3.11/site-packages/urllib3/util/url.py", line 425, in parse_url
    host, port = _HOST_PORT_RE.match(host_port).groups()  # type: ignore[union-attr]
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'groups'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.11/site-packages/requests/api.py", line 73, in get
    return request("get", url, params=params, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/requests/api.py", line 59, in request
    return session.request(method=method, url=url, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/requests/sessions.py", line 589, in request
    resp = self.send(prep, **send_kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/requests/sessions.py", line 703, in send
    r = adapter.send(request, **kwargs)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/requests/adapters.py", line 486, in send
    resp = conn.urlopen(
           ^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/urllib3/connectionpool.py", line 711, in urlopen
    parsed_url = parse_url(url)
                 ^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/urllib3/util/url.py", line 451, in parse_url
    raise LocationParseError(source_url) from e
urllib3.exceptions.LocationParseError: Failed to parse: //v:h

Environment

Python: 3.11

What Broke

Requests to URLs with leading slashes result in AttributeError due to parsing failure.

Why It Broke

Leading slashes in the URL path cause urllib3 to misinterpret the URL structure

Fix Options (Details)

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

pip install requests==2.32.0

When NOT to use: This fix is not applicable for URLs where leading slashes are intended for valid paths.

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/6644

First fixed release: 2.32.0

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

When NOT to Use This Fix

This fix is not applicable for URLs where leading slashes are intended for valid paths.

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.
Track RSS + object counts after deployments; alert on monotonic growth and GC pressure.
Add a long-running test that repeats the failing call path and asserts stable memory.

Version Compatibility Table

Version	Status
2.32.0	Fixed

Related Issues

No related fixes found.

Cluster: requests:configuration-error Requests hub Requests 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.

Requests Leading slash in uri followed by column fails (Fix)

The Fix

Why This Fix Works in Production

Why This Breaks in Prod

Proof / Evidence

Discussion

Failure Signature (Search String)

Error Message

Minimal Reproduction

Environment

What Broke

Why It Broke

Fix Options (Details)

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

Get updates

When NOT to Use This Fix

Verify Fix

Did This Fix Work in Your Case?

Prevention

Version Compatibility Table

Related Issues

Sources