Helix test runs are failing with "ModuleNotFoundError: No module named '_cffi_backend'" #6487
Description
Build
import pkg_resources
Traceback (most recent call last):
File "/tmp/helix/working/C8F90A73/p/reporter/run.py", line 13, in <module>
from test_results_reader import read_results
File "/private/tmp/helix/working/C8F90A73/p/reporter/test_results_reader/__init__.py", line 3, in <module>
from helix.public import TestResult, TestResultAttachment
File "/etc/helix/scripts/helix/public/__init__.py", line 5, in <module>
import helix.event
File "/etc/helix/scripts/helix/event.py", line 7, in <module>
import helix.logs
File "/etc/helix/scripts/helix/logs.py", line 11, in <module>
from helix.azure_utils import get_auth_credential
File "/etc/helix/scripts/helix/azure_utils.py", line 2, in <module>
from azure.identity import CertificateCredential, ClientAssertionCredential, ManagedIdentityCredential, DefaultAzureCredential
File "/etc/helix/scripts/azure/identity/__init__.py", line 10, in <module>
from ._credentials import (
...<19 lines>...
)
File "/etc/helix/scripts/azure/identity/_credentials/__init__.py", line 5, in <module>
from .authorization_code import AuthorizationCodeCredential
File "/etc/helix/scripts/azure/identity/_credentials/authorization_code.py", line 9, in <module>
from .._internal.aad_client import AadClient
File "/etc/helix/scripts/azure/identity/_internal/__init__.py", line 5, in <module>
from .aad_client import AadClient
File "/etc/helix/scripts/azure/identity/_internal/aad_client.py", line 11, in <module>
from .aad_client_base import AadClientBase
File "/etc/helix/scripts/azure/identity/_internal/aad_client_base.py", line 21, in <module>
from .aadclient_certificate import AadClientCertificate
File "/etc/helix/scripts/azure/identity/_internal/aadclient_certificate.py", line 7, in <module>
from cryptography import x509
File "/etc/helix/scripts/cryptography/x509/__init__.py", line 7, in <module>
from cryptography.x509 import certificate_transparency, verification
File "/etc/helix/scripts/cryptography/x509/certificate_transparency.py", line 8, in <module>
from cryptography.hazmat.bindings._rust import x509 as rust_x509
ModuleNotFoundError: No module named '_cffi_backend'
+ exit 1
['Microsoft.Extensions.FileProviders.Composite.Tests' END OF WORK ITEM LOG: Command exited with 1]
Build leg reported
Microsoft.Extensions.FileProviders.Composite.Tests.WorkItemExecution
Pull Request
Known issue core information
Fill out the known issue JSON section by following the step by step documentation on how to create a known issue
{
"ErrorMessage" : "ModuleNotFoundError: No module named '_cffi_backend'",
"BuildRetry": true,
"ErrorPattern": "",
"ExcludeConsoleLog": false
}@dotnet/dnceng
Release Note Category
- Feature changes/additions
- Bug fixes
- Internal Infrastructure Improvements
Release Note Description
Additional information about the issue reported
No response
Known issue validation
Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1354685
Error message validated: [ModuleNotFoundError: No module named '_cffi_backend']
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 3/27/2026 4:07:49 PM UTC
Report
| Build | Definition | Test | Pull Request |
|---|---|---|---|
| 1354685 | dotnet/runtime | System.Text.Encodings.Web.Tests.WorkItemExecution | dotnet/runtime#126191 |
| 1354405 | dotnet/sdk | dotnet-watch.Tests.dll.8.WorkItemExecution | dotnet/sdk#53580 |
| 1354132 | dotnet/runtime | ilasm_tests.WorkItemExecution | dotnet/runtime#126161 |
| 1353964 | dotnet/sdk | dotnet.Tests.dll.45.WorkItemExecution | dotnet/sdk#53453 |
Summary
| 24-Hour Hit Count | 7-Day Hit Count | 1-Month Count |
|---|---|---|
| 0 | 4 | 4 |