httpx uses deprecated ssl.PROTOCOL

The Fix

Upgrade to version 0.18.2 or later.

Based on closed encode/httpx issue #1670 · 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

@@ -897,32 +897,35 @@ def _send_handling_auth(
     ) -> Response:
         auth_flow = auth.sync_auth_flow(request)
-        request = next(auth_flow)
+        try:
+            request = next(auth_flow)

repro.py

_______________________________________________________________________ test_default_default_headers _______________________________________________________________________

    @pytest.mark.asyncio
    async def test_default_default_headers():
        config = Config(app=app, loop="asyncio", limit_max_requests=1)
        async with run_server(config):
          async with httpx.AsyncClient() as client:

tests/test_default_headers.py:18: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
venv/lib/python3.10/site-packages/httpx/_client.py:1242: in __init__
    self._transport = self._init_transport(
venv/lib/python3.10/site-packages/httpx/_client.py:1285: in _init_transport
    ssl_context = create_ssl_context(verify=verify, cert=cert, trust_env=trust_env)
venv/lib/python3.10/site-packages/httpx/_config.py:49: in create_ssl_context
    return SSLConfig(
venv/lib/python3.10/site-packages/httpx/_config.py:73: in __init__
    self.ssl_context = self.load_ssl_context()
venv/lib/python3.10/site-packages/httpx/_config.py:85: in load_ssl_context
    return self.load_ssl_context_verify()
venv/lib/python3.10/site-packages/httpx/_config.py:122: in load_ssl_context_verify
    context = self._create_default_ssl_context()
venv/lib/python3.10/site-packages/httpx/_config.py:156: in _create_default_ssl_context
    context = SSL.SSLContext(ssl.PROTOCOL_TLS)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

cls = <class 'ssl.SSLContext'>, protocol = ssl.PROTOCOL_TLS, args = (), kwargs = {}

    def __new__(cls, protocol=None, *args, **kwargs):
        if protocol is None:
            warnings.warn(
                "ssl module: "
                "SSLContext() without protocol argument is deprecated.",
                category=DeprecationWarning,
                stacklevel=2
            )
            protocol = PROTOCOL_TLS
      self = _SSLContext.__new__(cls, protocol)
E       DeprecationWarning: ssl module: PROTOCOL_TLS is deprecated

/usr/lib/python3.10/ssl.py:501: DeprecationWarning

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 0.18.2 or later.\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: uses deprecated ssl.PROTOCOL_TLS
Mechanism: Replaces the deprecated ssl.PROTOCOL_TLS with ssl.PROTOCOL_TLS_CLIENT to address the deprecation warning in Python 3.10.
Why the fix works: Replaces the deprecated ssl.PROTOCOL_TLS with ssl.PROTOCOL_TLS_CLIENT to address the deprecation warning in Python 3.10. (first fixed release: 0.18.2).

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 3.10 in real deployments (not just unit tests).
Production symptom (often without a traceback): uses deprecated ssl.PROTOCOL_TLS

Proof / Evidence

GitHub issue: #1670
Fix PR: https://github.com/encode/httpx/pull/1687
First fixed release: 0.18.2
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.39

Discussion

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

Jump to Sources Open on GitHub

“Could we start this off with a bit more context? I can see in the 3.10 release notes, that ssl.PROTOCOL_TLS becomes deprecated”

@lovelydinosaur · 2021-06-09 · source

“> Please create a ticket on BPO. https://bugs.python.org/issue44362”

@graingert · 2021-06-09 · source

Failure Signature (Search String)

uses deprecated ssl.PROTOCOL_TLS
ssl_context = create_ssl_context(verify=verify, cert=cert, trust_env=trust_env)

Copy-friendly signature

signature.txt

Failure Signature
-----------------
uses deprecated ssl.PROTOCOL_TLS
ssl_context = create_ssl_context(verify=verify, cert=cert, trust_env=trust_env)

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
uses deprecated ssl.PROTOCOL_TLS
ssl_context = create_ssl_context(verify=verify, cert=cert, trust_env=trust_env)

Minimal Reproduction

repro.py

_______________________________________________________________________ test_default_default_headers _______________________________________________________________________

    @pytest.mark.asyncio
    async def test_default_default_headers():
        config = Config(app=app, loop="asyncio", limit_max_requests=1)
        async with run_server(config):
          async with httpx.AsyncClient() as client:

tests/test_default_headers.py:18: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
venv/lib/python3.10/site-packages/httpx/_client.py:1242: in __init__
    self._transport = self._init_transport(
venv/lib/python3.10/site-packages/httpx/_client.py:1285: in _init_transport
    ssl_context = create_ssl_context(verify=verify, cert=cert, trust_env=trust_env)
venv/lib/python3.10/site-packages/httpx/_config.py:49: in create_ssl_context
    return SSLConfig(
venv/lib/python3.10/site-packages/httpx/_config.py:73: in __init__
    self.ssl_context = self.load_ssl_context()
venv/lib/python3.10/site-packages/httpx/_config.py:85: in load_ssl_context
    return self.load_ssl_context_verify()
venv/lib/python3.10/site-packages/httpx/_config.py:122: in load_ssl_context_verify
    context = self._create_default_ssl_context()
venv/lib/python3.10/site-packages/httpx/_config.py:156: in _create_default_ssl_context
    context = SSL.SSLContext(ssl.PROTOCOL_TLS)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

cls = <class 'ssl.SSLContext'>, protocol = ssl.PROTOCOL_TLS, args = (), kwargs = {}

    def __new__(cls, protocol=None, *args, **kwargs):
        if protocol is None:
            warnings.warn(
                "ssl module: "
                "SSLContext() without protocol argument is deprecated.",
                category=DeprecationWarning,
                stacklevel=2
            )
            protocol = PROTOCOL_TLS
      self = _SSLContext.__new__(cls, protocol)
E       DeprecationWarning: ssl module: PROTOCOL_TLS is deprecated

/usr/lib/python3.10/ssl.py:501: DeprecationWarning

Environment

Python: 3.10

Fix Options (Details)

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

Upgrade to version 0.18.2 or later.

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/encode/httpx/pull/1687

First fixed release: 0.18.2

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 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.
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
0.18.2	Fixed

Related Issues

No related fixes found.

Cluster: httpx:configuration-error All hubs All clusters

Related clusters: Data consistency Other Timeout

Sources

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

httpx uses deprecated ssl.PROTOCOL_TLS (Fix)