Block CORS for ajax paths by TomeHirata · Pull Request #20832 · mlflow/mlflow

TomeHirata · 2026-02-16T04:34:16Z

Related Issues/PRs

#20812

What changes are proposed in this pull request?

Fixed a CORS issue where the origin check is not enabled for ajax paths

How is this PR tested?

Existing unit/integration tests
New unit/integration tests
Manual tests

Does this PR require documentation update?

Does this PR require updating the MLflow Skills repository?

No. You can skip the rest of this section.
Yes. Please link the corresponding PR or explain how you plan to update it.

Release Notes

Is this a user-facing change?

No. You can skip the rest of this section.
Yes. Give a description of this change to be included in the release notes for MLflow users.

What component(s), interfaces, languages, and integrations does this PR affect?

Components

How should the PR be classified in the release notes? Choose one:

rn/none - No description will be included. The PR will be mentioned only by the PR number in the "Small Bugfixes and Documentation Updates" section
rn/breaking-change - The PR will be mentioned in the "Breaking Changes" section
rn/feature - A new user-facing feature worth mentioning in the release notes
rn/bug-fix - A user-facing bug fix worth mentioning in the release notes
rn/documentation - A user-facing documentation change worth mentioning in the release notes

Should this PR be included in the next patch release?

Yes should be selected for bug fixes, documentation updates, and other small changes. No should be selected for new features and larger changes. If you're unsure about the release classification of this PR, leave this unchecked to let the maintainers decide.

What is a minor/patch release?

Minor release: a release that increments the second part of the version number (e.g., 1.2.0 -> 1.3.0).
Bug fixes, doc updates and new features usually go into minor releases.
Patch release: a release that increments the third part of the version number (e.g., 1.2.0 -> 1.2.1).
Bug fixes and doc updates usually go into patch releases.

Yes (this PR will be cherry-picked and included in the next patch release)
No (this PR will be included in the next minor release)

Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>

github-actions · 2026-02-16T04:34:26Z

🛠 DevTools 🛠

Install mlflow from this PR

# mlflow
pip install git+https://github.com/mlflow/mlflow.git@refs/pull/20832/merge
# mlflow-skinny
pip install git+https://github.com/mlflow/mlflow.git@refs/pull/20832/merge#subdirectory=libs/skinny

For Databricks, use the following command:

%sh curl -LsSf https://raw.githubusercontent.com/mlflow/mlflow/HEAD/dev/install-skinny.sh | sh -s pull/20832/merge

github-actions · 2026-02-16T04:44:08Z

Documentation preview for ed56978 is available at:

https://pr-20832--mlflow-docs-preview.netlify.app/docs/latest/

More info

Ignore this comment if this PR does not change the documentation.
The preview is updated when a new commit is pushed to this PR.
This comment was created by this workflow run.
The documentation was built by this workflow run.

B-Step62

LGTM

mlflow/server/fastapi_security.py

Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>

Copilot

Pull request overview

This pull request addresses a critical CORS (Cross-Origin Resource Sharing) security vulnerability where origin validation was not being applied to /ajax-api/ endpoints. The vulnerability allowed unauthorized cross-origin requests to these endpoints, which are extensively used by the MLflow frontend for API calls.

Changes:

Extended CORS origin checking to include /ajax-api/ path prefix in addition to /api/ prefix
Fixed FastAPI CORSMiddleware configuration to properly restrict origins instead of allowing all origins by default
Added comprehensive test coverage for the security fix

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
`mlflow/server/security_utils.py`	Added `AJAX_API_PATH_PREFIX` constant and updated `is_api_endpoint()` to check for both `/api/` and `/ajax-api/` prefixes
`mlflow/server/fastapi_security.py`	Fixed critical issue where `allow_origins` was set to `["*"]` by default; now properly uses configured origins plus localhost patterns
`tests/server/test_security.py`	Added test for `is_api_endpoint()` with ajax paths, added FastAPI CORS tests for localhost origins and configured origins, updated OPTIONS request test to expect 204 status
`tests/server/conftest.py`	Added `fastapi_client` fixture and updated test endpoint paths to use realistic API paths

Copilot · 2026-02-16T05:39:03Z

tests/server/test_security.py

+        "/api/2.0/mlflow/experiments/list",
+        headers={"Host": "localhost", "Origin": "http://evil.com"},
+    )
+    assert response.headers.get("access-control-allow-origin") is None


The FastAPI CORS tests only verify that GET requests from unauthorized origins don't receive CORS headers, but they don't test that POST requests from unauthorized origins are actually blocked with a 403 status. This is a critical security behavior that should be explicitly tested. Consider adding a test case that sends a POST request from an unauthorized origin to a FastAPI endpoint and verifies it returns 403 status with appropriate error message.

Suggested change

assert response.headers.get("access-control-allow-origin") is None

assert response.headers.get("access-control-allow-origin") is None

# Verify that POST requests from an unauthorized origin are blocked

response = client.post(

"/api/2.0/mlflow/experiments/list",

headers={"Host": "localhost", "Origin": "http://evil.com"},

)

assert response.status_code == 403

# Ensure an error message is returned

error_detail = response.json().get("detail")

assert isinstance(error_detail, str) and error_detail

Copilot · 2026-02-16T05:39:04Z

tests/server/test_security.py

+def test_is_api_endpoint(path, expected):
+    assert is_api_endpoint(path) == expected
+
+


Consider adding an explicit test case for CORS blocking on /ajax-api/ paths. While test_is_api_endpoint() verifies that /ajax-api/ paths are recognized as API endpoints, there's no direct test similar to test_cors_protection that verifies POST requests from unauthorized origins to /ajax-api/ endpoints are actually blocked with a 403 status. This would provide stronger verification that the security fix works end-to-end.

Suggested change

def test_fastapi_cors_blocks_unauthorized_origin_on_ajax_api(fastapi_client):

response = fastapi_client.post(

"/ajax-api/2.0/mlflow/experiments/list",

headers={"Host": "localhost", "Origin": "http://evil.com"},

)

assert response.status_code == 403

Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>

Block CORS for ajax paths

033fb60

Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>

Copilot AI review requested due to automatic review settings February 16, 2026 04:34

github-actions bot added the size/M label Feb 16, 2026

TomeHirata requested review from B-Step62 and removed request for Copilot February 16, 2026 04:34

github-actions bot added v3.10.0 area/build Build and test infrastructure for MLflow rn/bug-fix Mention under Bug Fixes in Changelogs. labels Feb 16, 2026

TomeHirata added team-review Trigger a team review request and removed rn/bug-fix Mention under Bug Fixes in Changelogs. area/build Build and test infrastructure for MLflow v3.10.0 size/M labels Feb 16, 2026

github-actions bot requested review from harupy and serena-ruan February 16, 2026 04:34

Copilot started reviewing on behalf of TomeHirata February 16, 2026 04:34 View session

TomeHirata added the rn/bug-fix Mention under Bug Fixes in Changelogs. label Feb 16, 2026

B-Step62 approved these changes Feb 16, 2026

View reviewed changes

mlflow/server/fastapi_security.py Show resolved Hide resolved

comment

ed56978

Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>

Copilot AI review requested due to automatic review settings February 16, 2026 05:34

TomeHirata enabled auto-merge February 16, 2026 05:34

github-actions bot added the v3.10.0 label Feb 16, 2026

Copilot started reviewing on behalf of TomeHirata February 16, 2026 05:34 View session

Copilot AI reviewed Feb 16, 2026

View reviewed changes

TomeHirata added this pull request to the merge queue Feb 16, 2026

Merged via the queue into mlflow:master with commit 8f9c8a5 Feb 16, 2026
54 checks passed

TomeHirata deleted the fix/cors-ajax branch February 16, 2026 06:18

github-actions bot added the size/M label Feb 16, 2026

daniellok-db pushed a commit to daniellok-db/mlflow that referenced this pull request Feb 20, 2026

Block CORS for ajax paths (mlflow#20832)

90af4ea

Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>

daniellok-db pushed a commit that referenced this pull request Feb 20, 2026

Block CORS for ajax paths (#20832)

4b9fa88

Signed-off-by: Tomu Hirata <tomu.hirata@gmail.com>

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Block CORS for ajax paths#20832

Block CORS for ajax paths#20832
TomeHirata merged 2 commits intomlflow:masterfrom
TomeHirata:fix/cors-ajax

TomeHirata commented Feb 16, 2026

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github-actions bot commented Feb 16, 2026

Install mlflow from this PR

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github-actions bot commented Feb 16, 2026 •

edited

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-    assert response.headers.get("access-control-allow-origin") is None
+    assert response.headers.get("access-control-allow-origin") is None
+    # Verify that POST requests from an unauthorized origin are blocked
+    response = client.post(
+        "/api/2.0/mlflow/experiments/list",
+        headers={"Host": "localhost", "Origin": "http://evil.com"},
+    )
+    assert response.status_code == 403
+    # Ensure an error message is returned
+    error_detail = response.json().get("detail")
+    assert isinstance(error_detail, str) and error_detail

		def test_is_api_endpoint(path, expected):
		assert is_api_endpoint(path) == expected

+def test_fastapi_cors_blocks_unauthorized_origin_on_ajax_api(fastapi_client):
+    response = fastapi_client.post(
+        "/ajax-api/2.0/mlflow/experiments/list",
+        headers={"Host": "localhost", "Origin": "http://evil.com"},
+    )
+    assert response.status_code == 403

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TomeHirata commented Feb 16, 2026

Related Issues/PRs

What changes are proposed in this pull request?

How is this PR tested?

Does this PR require documentation update?

Does this PR require updating the MLflow Skills repository?

Release Notes

Is this a user-facing change?

What component(s), interfaces, languages, and integrations does this PR affect?

How should the PR be classified in the release notes? Choose one:

Should this PR be included in the next patch release?

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github-actions bot commented Feb 16, 2026

Install mlflow from this PR

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Pull request overview

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github-actions bot commented Feb 16, 2026 •

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