az acr login regression in 2.87.0 on AzureML compute MSI/SSO

[elonp]

Describe the bug

az acr login regression in 2.87.0 on AzureML compute MSI/SSO

Summary

az acr login appears to regress between Azure CLI 2.81.0 and 2.87.0 on an AzureML Compute
Instance using az login --identity.

On the same AzureML compute instance, Azure CLI 2.81.0 succeeds with az acr login, while
Azure CLI 2.87.0 fails. A direct ACR OAuth /oauth2/exchange using the ARM access token succeeds,
so this does not appear to be an ACR RBAC issue.

Repro commands

az login --identity
az acr login -n $ACR

Observed behavior with Azure CLI 2.87.0

az account get-access-token --resource https://management.azure.com/
=> succeeds

az account get-access-token --resource https://containerregistry.azure.net
=> fails:
ERROR: {'error': 'SSO failure, to mitigated it please try to click Jupyter/JupyterLab.'}
Run the command below to authenticate interactively; additional arguments may be added as needed:
az logout
az login

az acr login -n $ACR--expose-token
=> fails:
WARNING: Unable to get AAD authorization tokens with message: {'error': 'SSO failure, to mitigated it please try to click Jupyter/JupyterLab.'}
WARNING: Unable to get admin user credentials with message: Admin user is disabled.
ERROR: Unable to authenticate using AAD or admin login credentials. Please specify both username and password in non-interactive mode.

az acr login -n $ACR
=> fails with the same warnings/errors

Expected behavior / behavior with Azure CLI 2.81.0

az account get-access-token --resource https://containerregistry.azure.net
=> fails with the same SSO error

az acr login -n $ACR --expose-token
=> succeeds and returns an accessToken

az acr login -n amlacraepije663sbqi
=> Login Succeeded

Installing Azure CLI 2.81.0 into an isolated venv on the same machine makes az acr login work:

python -m venv ~/azcli-2.81-test
source ~/azcli-2.81-test/bin/activate
pip install 'azure-cli==2.81.0'
az login --identity
az acr login -n $ACR --expose-token
az acr login -n $ACR

Additional evidence

A direct ACR OAuth exchange using the ARM access token succeeds on the failing Azure CLI 2.87.0
machine:

ARM token: ok
ACR OAuth exchange with ARM token: {"exchange": "ok", "has_refresh_token": true}

The direct exchange is:

POST https://$ACR.azurecr.io/oauth2/exchange

grant_type=access_token
service=$ACR.azurecr.io
tenant=<tenant-id>
access_token=<ARM access token for https://management.azure.com/>

Using the returned refresh token with Docker succeeds:

printf '%s' "$REFRESH_TOKEN" | docker login $ACR.azurecr.io \
  -u 00000000-0000-0000-0000-000000000000 \
  --password-stdin

Result:

Login Succeeded

This suggests ACR authorization and registry-side OAuth exchange are working, but the Azure CLI
2.87.0 az acr login implementation is not using, or is no longer falling back to, the ARM-token
exchange path that works in Azure CLI 2.81.0.

Suspected regression area

Likely area: built-in ACR command module / auth path used by az acr login.

The ACR module files differ between working 2.81.0 and failing 2.87.0 installations:

azure.cli.command_modules.acr custom.py: different SHA256
azure.cli.command_modules.acr _docker_utils.py: different SHA256
azure.cli.command_modules.acr _constants.py: different SHA256

The suspected behavior change is in how az acr login chooses between:

1. acquiring an AAD token for https://containerregistry.azure.net, and
2. exchanging an ARM token at https://<registry>/oauth2/exchange.

In this AzureML MSI/SSO environment, path (1) fails but path (2) succeeds. Azure CLI 2.81.0 still
logs in successfully; Azure CLI 2.87.0 fails.

Related command

az login --identity
az acr login -n $ACR

Errors

ERROR: {'error': 'SSO failure, to mitigated it please try to click Jupyter/JupyterLab.'}
Run the command below to authenticate interactively; additional arguments may be added as needed:
az logout
az login

Issue script & Debug output

(azureml_py38) azureuser@elonp2:~/repos/kblam/collabs/ct/image$ az acr login -n $ACR --debug
cli.knack.cli: Command arguments: ['acr', 'login', '-n', 'amlacraepije663sbqi', '--debug']
cli.knack.cli: init debug log:
Enable color in terminal.
cli.knack.cli: Event: Cli.PreExecute []
cli.knack.cli: Event: CommandParser.OnGlobalArgumentsCreate [<function CLILogging.on_global_arguments at 0x7ba1d766fac0>, <function OutputProducer.on_global_arguments at 0x7ba1d75dd990>, <function CLIQuery.on_global_arguments at 0x7ba1d740ad40>]
cli.knack.cli: Event: CommandInvoker.OnPreCommandTableCreate []
cli.azure.cli.core: Using packaged command index for profile 'latest'.
cli.azure.cli.core: Found installed extension 'azure-cli-ml' (azext_ml).
cli.azure.cli.core: Blending packaged core index with local extension index.
cli.azure.cli.core: Modules found from index for 'acr': ['azure.cli.command_modules.acr']
cli.azure.cli.core: Loading command modules...
cli.azure.cli.core: Loaded command modules in parallel:
cli.azure.cli.core: Name Load Time Groups Commands
cli.azure.cli.core: acr 0.055 36 150
cli.azure.cli.core: Total (1) 0.057 36 150
cli.azure.cli.core: These extensions are not installed and will be skipped: ['azext_ai_examples', 'azext_next']
cli.azure.cli.core: Loading extensions:
cli.azure.cli.core: Name Load Time Groups Commands Directory
cli.azure.cli.core: Total (0) 0.000 0 0
cli.azure.cli.core: Loaded 36 groups, 150 commands.
cli.azure.cli.core: Found a match in the command table.
cli.azure.cli.core: Raw command : acr login
cli.azure.cli.core: Command table: acr login
cli.knack.cli: Event: CommandInvoker.OnPreCommandTableTruncate [<function AzCliLogging.init_command_file_logging at 0x7ba1d7160a60>]
cli.azure.cli.core.azlogging: metadata file logging enabled - writing logs to '/home/azureuser/.azure/commands/2026-07-03.10-41-21.acr_login.85242.log'.
az_command_data_logger: command args: acr login -n {} --debug
cli.knack.cli: Event: CommandInvoker.OnPreArgumentLoad [<function register_global_subscription_argument..add_subscription_parameter at 0x7ba1d7179d80>]
cli.knack.commands: Configured default 'eyeson.heron.prod.e02fd9de-d296-41d1-bd86-efc4853e27da' for arg resource_group_name
cli.knack.cli: Event: CommandInvoker.OnPostArgumentLoad []
cli.knack.cli: Event: CommandInvoker.OnPostCommandTableCreate [<function register_ids_argument..add_ids_arguments at 0x7ba1d71a16c0>, <function register_global_policy_argument..add_global_policy_argument at 0x7ba1d71a17e0>, <function register_cache_arguments..add_cache_arguments at 0x7ba1d71a1870>, <function register_upcoming_breaking_change_info..update_breaking_change_info at 0x7ba1d71a1900>]
cli.knack.cli: Event: CommandInvoker.OnCommandTableLoaded []
cli.knack.cli: Event: CommandInvoker.OnPreParseArgs []
cli.knack.cli: Event: CommandInvoker.OnPostParseArgs [<function OutputProducer.handle_output_argument at 0x7ba1d75dda20>, <function CLIQuery.handle_query_parameter at 0x7ba1d740add0>, <function register_ids_argument..parse_ids_arguments at 0x7ba1d71a1750>]
cli.azure.cli.core.commands.client_factory: Getting management service client client_type=ContainerRegistryManagementClient
cli.azure.cli.core.auth.credential_adaptor: CredentialAdaptor.get_token_info: scopes=('https://management.core.windows.net//.default',), options={}
cli.azure.cli.core.auth.msal_credentials: ManagedIdentityCredential.acquire_token: scopes=['https://management.core.windows.net//.default'], kwargs={}
msal.managed_identity: Obtaining token via managed identity on Azure Machine Learning
urllib3.connectionpool: Starting new HTTP connection (1): 127.0.0.1:46808
urllib3.connectionpool: http://127.0.0.1:46808 "GET /MSI/auth?api-version=2017-09-01&resource=https%3A%2F%2Fmanagement.core.windows.net%2F HTTP/1.1" 200 None
msal.token_cache: event={
"client_id": null,
"data": {},
"params": {},
"response": {
"access_token": "***",
"expires_in": 2867,
"resource": "https://management.core.windows.net/",
"token_type": "Bearer"
},
"scope": [
"https://management.core.windows.net/"
],
"token_endpoint": "https://localhost/managed_identity"
}
cli.azure.cli.core.sdk.policies: Request URL: 'https://management.azure.com/subscriptions/08047947-f71e-4462-a09d-266e3d34c431/resourceGroups/eyeson.heron.prod.e02fd9de-d296-41d1-bd86-efc4853e27da/providers/Microsoft.ContainerRegistry/registries/amlacraepije663sbqi?api-version=2026-01-01-preview'
cli.azure.cli.core.sdk.policies: Request method: 'GET'
cli.azure.cli.core.sdk.policies: Request headers:
cli.azure.cli.core.sdk.policies: 'Accept': 'application/json'
cli.azure.cli.core.sdk.policies: 'x-ms-client-request-id': 'bb55ace4-76cb-11f1-b4c5-0022480137ed'
cli.azure.cli.core.sdk.policies: 'CommandName': 'acr login'
cli.azure.cli.core.sdk.policies: 'ParameterSetName': '-n --debug'
cli.azure.cli.core.sdk.policies: 'User-Agent': 'AZURECLI/2.87.0 (PIP) azsdk-python-core/1.39.0 Python/3.10.0 (Linux-6.8.0-1059-azure-x86_64-with-glibc2.35)'
cli.azure.cli.core.sdk.policies: 'Authorization': ''
cli.azure.cli.core.sdk.policies: Request body:
cli.azure.cli.core.sdk.policies: This request has no body
urllib3.connectionpool: Starting new HTTPS connection (1): management.azure.com:443
urllib3.connectionpool: https://management.azure.com:443 "GET /subscriptions/08047947-f71e-4462-a09d-266e3d34c431/resourceGroups/eyeson.heron.prod.e02fd9de-d296-41d1-bd86-efc4853e27da/providers/Microsoft.ContainerRegistry/registries/amlacraepije663sbqi?api-version=2026-01-01-preview HTTP/1.1" 200 1582
cli.azure.cli.core.sdk.policies: Response status: 200
cli.azure.cli.core.sdk.policies: Response headers:
cli.azure.cli.core.sdk.policies: 'Cache-Control': 'no-cache'
cli.azure.cli.core.sdk.policies: 'Pragma': 'no-cache'
cli.azure.cli.core.sdk.policies: 'Content-Length': '1582'
cli.azure.cli.core.sdk.policies: 'Content-Type': 'application/json; charset=utf-8'
cli.azure.cli.core.sdk.policies: 'Expires': '-1'
cli.azure.cli.core.sdk.policies: 'Strict-Transport-Security': 'max-age=31536000; includeSubDomains'
cli.azure.cli.core.sdk.policies: 'api-supported-versions': '2026-01-01-preview'
cli.azure.cli.core.sdk.policies: 'x-ms-ratelimit-remaining-subscription-reads': '1099'
cli.azure.cli.core.sdk.policies: 'x-ms-ratelimit-remaining-subscription-global-reads': '16499'
cli.azure.cli.core.sdk.policies: 'x-ms-request-id': 'f8a0723f-70ae-4a26-bc44-4ac3a78c7de0'
cli.azure.cli.core.sdk.policies: 'x-ms-correlation-request-id': 'f8a0723f-70ae-4a26-bc44-4ac3a78c7de0'
cli.azure.cli.core.sdk.policies: 'x-ms-routing-request-id': 'EASTUS2:20260703T104122Z:f8a0723f-70ae-4a26-bc44-4ac3a78c7de0'
cli.azure.cli.core.sdk.policies: 'X-Content-Type-Options': 'nosniff'
cli.azure.cli.core.sdk.policies: 'X-Cache': 'CONFIG_NOCACHE'
cli.azure.cli.core.sdk.policies: 'X-MSEdge-Ref': 'Ref A: 9539786F689A4F4E9D71A27E71C381D3 Ref B: AMS231032609053 Ref C: 2026-07-03T10:41:22Z'
cli.azure.cli.core.sdk.policies: 'Date': 'Fri, 03 Jul 2026 10:41:22 GMT'
cli.azure.cli.core.sdk.policies: Response content:
cli.azure.cli.core.sdk.policies: {"sku":{"name":"Basic","tier":"Basic"},"type":"Microsoft.ContainerRegistry/registries","id":"/subscriptions/08047947-f71e-4462-a09d-266e3d34c431/resourceGroups/EYESON.HERON.PROD.e02fd9de-d296-41d1-bd86-efc4853e27da/providers/Microsoft.ContainerRegistry/registries/amlacraepije663sbqi","name":"amlacraepije663sbqi","location":"eastus2","tags":{},"systemData":{"createdBy":"54caada3-19bd-4b50-9eb8-70f6f6d4b32e","createdByType":"Application","createdAt":"2026-02-04T19:59:01.9248036+00:00","lastModifiedBy":"54caada3-19bd-4b50-9eb8-70f6f6d4b32e","lastModifiedByType":"Application","lastModifiedAt":"2026-06-18T03:53:06.5129871+00:00"},"properties":{"loginServer":"amlacraepije663sbqi.azurecr.io","creationDate":"2026-02-04T19:59:01.9248036Z","provisioningState":"Succeeded","adminUserEnabled":false,"policies":{"quarantinePolicy":{"status":"disabled"},"trustPolicy":{"type":"Notary","status":"disabled"},"retentionPolicy":{"days":7,"status":"disabled"},"exportPolicy":{"status":"enabled"},"azureADAuthenticationAsArmPolicy":{"status":"enabled"},"softDeletePolicy":{"retentionDays":7,"status":"disabled"}},"encryption":{"status":"disabled"},"dataEndpointEnabled":false,"regionalEndpoints":"Disabled","dataEndpointHostNames":[],"regionalEndpointHostNames":[],"endpointProtocol":"IPv4","privateEndpointConnections":[],"publicNetworkAccess":"Enabled","networkRuleBypassOptions":"AzureServices","networkRuleBypassAllowedForTasks":false,"zoneRedundancy":"Disabled","metadataSearch":"Disabled","roleAssignmentMode":"LegacyRegistryPermissions","autoGeneratedDomainNameLabelScope":"Unsecure"}}
cli.azure.cli.command_modules.acr._docker_utils: 2026-07-03 10:41:22.495061 Sending a HTTP Get request to https://amlacraepije663sbqi.azurecr.io/v2/
urllib3.connectionpool: Starting new HTTPS connection (1): amlacraepije663sbqi.azurecr.io:443
urllib3.connectionpool: https://amlacraepije663sbqi.azurecr.io:443 "GET /v2/ HTTP/1.1" 401 149
cli.azure.cli.command_modules.acr._docker_utils: Attempting to retrieve AAD refresh token...
cli.azure.cli.command_modules.acr._docker_utils: 2026-07-03 10:41:22.770695 Sending a HTTP Get request to https://amlacraepije663sbqi.azurecr.io/v2/
urllib3.connectionpool: Starting new HTTPS connection (1): amlacraepije663sbqi.azurecr.io:443
urllib3.connectionpool: https://amlacraepije663sbqi.azurecr.io:443 "GET /v2/ HTTP/1.1" 401 149
cli.azure.cli.core.auth.msal_credentials: ManagedIdentityCredential.acquire_token: scopes=['https://containerregistry.azure.net/.default'], kwargs={}
msal.managed_identity: Obtaining token via managed identity on Azure Machine Learning
urllib3.connectionpool: Starting new HTTP connection (1): 127.0.0.1:46808
urllib3.connectionpool: http://127.0.0.1:46808 "GET /MSI/auth?api-version=2017-09-01&resource=https%3A%2F%2Fcontainerregistry.azure.net HTTP/1.1" 404 80
cli.azure.cli.core.auth.util: MSAL error: {'error': 'invalid_scope', 'error_description': "{'error': 'SSO failure, to mitigated it please try to click Jupyter/JupyterLab.'}"}
cli.azure.cli.command_modules.acr._docker_utils: Unable to get AAD authorization tokens with message: {'error': 'SSO failure, to mitigated it please try to click Jupyter/JupyterLab.'}
cli.azure.cli.command_modules.acr._docker_utils: Unable to get admin user credentials with message: Admin user is disabled.
Username:

Expected behavior

az acr login -n $ACR should succeed in logging-in to the ACR.

Environment Summary

azure-cli 2.87.0

core 2.87.0
telemetry 1.1.0

Extensions:
azure-cli-ml 1.41.0
ml 2.43.0

Dependencies:
msal 1.36.0
azure-mgmt-resource 24.0.0

Python location '/anaconda/envs/azureml_py38/bin/python'
Config directory '/home/azureuser/.azure'
Extensions directory '/opt/az/extensions'

Python (Linux) 3.10.0 | packaged by conda-forge | (default, Nov 20 2021, 02:24:10) [GCC 9.4.0]

Legal docs and information: aka.ms/AzureCliLegal

Your CLI is up-to-date.

Additional context

Compute instance software version
Linux 26.06.15 (current)

[a0x1ab]

Bug Analysis

az acr login regressed between Azure CLI 2.81.0 and 2.87.0 when running on an AzureML
Compute Instance authenticated via az login --identity (MSI/SSO environment).

• In this environment, acquiring an AAD token directly for https://containerregistry.azure.net
  fails with an SSO error (SSO failure, to mitigated it please try to click Jupyter/JupyterLab.).
• However, exchanging an ARM access token (https://management.azure.com/) at the registry's
  /oauth2/exchange endpoint succeeds, and the resulting refresh token works fine with docker login.
• Azure CLI 2.81.0's az acr login still succeeds in this environment (it falls back to / uses the
  ARM-token exchange path), while 2.87.0 fails, suggesting a change in
  azure.cli.command_modules.acr (custom.py, _docker_utils.py, _constants.py) removed or
  altered the fallback behavior between acquiring a registry-scoped AAD token vs. exchanging an
  ARM token.

Investigation focus:

• Diff _docker_utils.py/custom.py/_constants.py in src/azure-cli/azure/cli/command_modules/acr/
  between the 2.81.0 and 2.87.0 releases to find where the ARM-token exchange fallback was
  removed/changed for az acr login.
• Ensure az acr login falls back to exchanging the ARM access token at
  POST https://<registry>.azurecr.io/oauth2/exchange (grant_type=access_token) when acquiring
  a registry-scoped AAD token (https://containerregistry.azure.net) fails, particularly for
  MSI/managed-identity credentials.
• Add/adjust unit tests covering the ARM-token exchange fallback path for az acr login with an
  MSI/service-principal credential.

Repro:

az login --identity
az acr login -n $ACR

Expected: az acr login succeeds via ARM-token exchange fallback, matching 2.81.0 behavior.
Actual (2.87.0): Fails with Unable to get AAD authorization tokens / SSO error, no fallback
to the ARM token exchange path.

Use this EXACT PR title: [ACR] Fix #33698: az acr login: Fix ARM token exchange fallback for AzureML MSI/SSO

PR title & description format (required)

This repo enforces a PR format (guide). Please author the PR exactly as follows or CI's Check the Format of Pull Request Title and Content will fail.

Use this EXACT PR title (copy verbatim, do not reword):

[ACR] Fix #33698: `az acr login`: Fix ARM token exchange fallback for AzureML MSI/SSO

Keep the backticks around the command and the Fix #33698: prefix. You may only adjust the wording after the command (the final summary) if the fix changes; the [ACR] prefix, issue link, and backticked command must stay.

Description — follow the PR template and fill in:

• Link the issue — start the Description with a closing keyword so the PR auto-links and closes it: Fixes #33698.
• Related command — the az ... command this affects.
• Description (mandatory) — why the bug happens, what you changed, and the resulting behavior.
• Testing Guide — example command(s) showing the fix works.
• History Notes — leave the title to drive the history note, or add extra lines in the same format (component in brackets + the command in backticks), e.g. [ACR] `az <command>`: <note>.
• Keep the template checklist and tick the items you've satisfied.

---

Posted by agent-assist (autonomous bug-fix pipeline).