httpx SSL handshake failed on verifying the certificate

The Fix

Upgrade to version 0.7.3 or later.

Based on closed encode/httpx issue #376 · 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

@@ -107,13 +107,6 @@ def __init__(
             self.base_url = URL(base_url)
 
-        if proxies is None and trust_env:
-            proxies = typing.cast(ProxiesTypes, get_environment_proxies())
-

repro.py

import httpx
client = httpx.Client(proxies={
    "http": "http://192.168.1.78:8888",
    "https": "http://192.168.1.78:8888",

})


client_cer = r'C:\Users\localhost\Documents\123.pem'
request = client.get("http://whoer.net",verify=client_cer)

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 0.7.3 or later.\nWhen NOT to use: This fix should not be used if the proxy does not support certificate verification.\n\n

Why This Fix Works in Production

Trigger: SSL handshake failed on verifying the certificate
Mechanism: The Client configuration was not properly propagated to the HTTPProxy, causing certificate verification to fail
Why the fix works: Propagates the Client configuration to the HTTPProxy, ensuring that certificates specified via the 'verify' parameter are correctly utilized. (first fixed release: 0.7.3).

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 Client configuration was not properly propagated to the HTTPProxy, causing certificate verification to fail
Surfaces as: SSL handshake failed on verifying the certificate

Proof / Evidence

GitHub issue: #376
Fix PR: https://github.com/encode/httpx/pull/377
First fixed release: 0.7.3
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.30

Discussion

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

Jump to Sources Open on GitHub

“how i can make sure my code is going through line 129 with my client_cer variable? Im not experienced coding but if you tell me…”

@qwerty32123 · 2019-09-23 · source

“Could you try running that script with HTTPX_DEBUG=1 set as an environment variable? I can't see why TLS would be getting used unless the website…”

@sethmlarson · 2019-09-23 · source

“Like this: $ HTTPX_DEBUG=1 python run_script.py from the command line.”

@sethmlarson · 2019-09-23 · source

“i dont know if i did it good i did in windows machine, i can send you certificate if you want or whatever. cmd /c…”

@qwerty32123 · 2019-09-24 · source

Failure Signature (Search String)

SSL handshake failed on verifying the certificate

Error Message

Stack trace

error.txt

Error Message
-------------
SSL handshake failed on verifying the certificate
protocol: <asyncio.sslproto.SSLProtocol object at 0x0000020CDCD7E470>
transport: <_SelectorSocketTransport fd=768 read=polling write=<idle, bufsize=0>>
Traceback (most recent call last):
  File "C:\Users\localhost\AppData\Local\Programs\Python\Python37\lib\asyncio\sslproto.py", line 625, in _on_handshake_complete
    raise handshake_exc
  File "C:\Users\localhost\AppData\Local\Programs\Python\Python37\lib\asyncio\sslproto.py", line 189, in feed_ssldata
    self._sslobj.do_handshake()
  File "C:\Users\localhost\AppData\Local\Programs\Python\Python37\lib\ssl.py", line 763, in do_handshake
    self._sslobj.do_handshake()
ssl.SSLCertVerificationError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: self signed certificate in certificate chain (_ssl.c:1056)
SSL error in data received
protocol: <asyncio.sslproto.SSLProtocol object at 0x0000020CDCD7E470>
transport: <_SelectorSocketTransport closing fd=768 read=idle write=<idle, bufsize=0>>
Traceback (most recent call last):
  File "C:\Users\localhost\AppData\Local\Programs\Python\Python37\lib\asyncio\sslproto.py", line 526, in data_received
    ssldata, appdata = self._sslpipe.feed_ssldata(data)
  File "C:\Users\localhost\AppData\Local\Programs\Python\Python37\lib\asyncio\sslproto.py", line 189, in feed_ssldata
    self._sslobj.do_handshake()
  File "C:\Users\localhost\AppD
... (truncated) ...

Stack trace

error.txt

Error Message
-------------
C:\Users\localhost\PycharmProjects\TribalW_Test_Env\Basic\network\client>cmd /c "set HTTPX_DEBUG=1 && python  C:\Users\localhost\PycharmProjects\TribalW_Test_Env\Basic\tests\httpx\proxy_test.py"
SSL handshake failed on verifying the certificate
protocol: <asyncio.sslproto.SSLProtocol object at 0x000001261B0329E8>
transport: <_SelectorSocketTransport fd=636 read=polling write=<idle, bufsize=0>>
Traceback (most recent call last):
  File "C:\Users\localhost\AppData\Local\Programs\Python\Python37\lib\asyncio\sslproto.py", line 625, in _on_handshake_complete
    raise handshake_exc
  File "C:\Users\localhost\AppData\Local\Programs\Python\Python37\lib\asyncio\sslproto.py", line 189, in feed_ssldata
    self._sslobj.do_handshake()
  File "C:\Users\localhost\AppData\Local\Programs\Python\Python37\lib\ssl.py", line 763, in do_handshake
    self._sslobj.do_handshake()
ssl.SSLCertVerificationError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: self signed certificate in certificate chain (_ssl.c:1056)
SSL error in data received
protocol: <asyncio.sslproto.SSLProtocol object at 0x000001261B0329E8>
transport: <_SelectorSocketTransport closing fd=636 read=idle write=<idle, bufsize=0>>
Traceback (most recent call last):
  File "C:\Users\localhost\AppData\Local\Programs\Python\Python37\lib\asyncio\sslproto.py", line 526, in data_received
    ssldata, appdata = self._sslpipe.feed_
... (truncated) ...

Minimal Reproduction

repro.py

import httpx
client = httpx.Client(proxies={
    "http": "http://192.168.1.78:8888",
    "https": "http://192.168.1.78:8888",

})


client_cer = r'C:\Users\localhost\Documents\123.pem'
request = client.get("http://whoer.net",verify=client_cer)

What Broke

Users experienced SSL handshake failures when attempting to verify certificates through a proxy.

Why It Broke

The Client configuration was not properly propagated to the HTTPProxy, causing certificate verification to fail

Fix Options (Details)

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

Upgrade to version 0.7.3 or later.

When NOT to use: This fix should not be used if the proxy does not support certificate verification.

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/377

First fixed release: 0.7.3

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

When NOT to Use This Fix

This fix should not be used if the proxy does not support certificate verification.

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
0.7.3	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 SSL handshake failed on verifying the certificate (Fix)