Vulnerability-Lookup

CVE-2026-45349 (GCVE-0-2026-45349)

Vulnerability from cvelistv5 – Published: 2026-05-15 19:20 – Updated: 2026-05-19 12:41

Title

Open WebUI: Broken Access Control for Completions API

Summary

Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.0, a user just needs to use the API endpoint: /api/chat/completions with their own API key (generated in OWUI) and the Chat ID of another user to continue the conversation of the other user. This vulnerability is fixed in 0.9.0.

Severity

7.1 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N

CWE

CWE-639 - Authorization Bypass Through User-Controlled Key

Assigner

GitHub_M

References

1 reference

URL	Tags
https://github.com/open-webui/open-webui/security…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version
open-webui	open-webui	Affected: < 0.9.0

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-45349

Vulnerability from fkie_nvd - Published: 2026-05-15 20:16 - Updated: 2026-05-19 14:16

Severity

7.1 (High) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/open-webui/open-webui/security/advisories/GHSA-gfm2-xm6c-37qc	Exploit, Mitigation, Vendor Advisory
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/open-webui/open-webui/security/advisories/GHSA-gfm2-xm6c-37qc	Exploit, Mitigation, Vendor Advisory

Impacted products

	Vendor	Product	Version
	openwebui	open_webui	*

JSON

To clipboard

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          "cpeMatch": [
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              "criteria": "cpe:2.3:a:openwebui:open_webui:*:*:*:*:*:*:*:*",
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      "lang": "en",
      "value": "Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.0, a user just needs to use the API endpoint: /api/chat/completions with their own API key (generated in OWUI) and the Chat ID of another user to continue the conversation of the other user. This vulnerability is fixed in 0.9.0."
    }
  ],
  "id": "CVE-2026-45349",
  "lastModified": "2026-05-19T14:16:45.840",
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GHSA-GFM2-XM6C-37QC

Vulnerability from github – Published: 2026-05-14 20:24 – Updated: 2026-05-15 23:54

Summary

Open WebUI has Broken Access Control for Completions API

Details

Summary

Any user X can continue the conversation of any other user Y, as long as the Chat ID of Y is known. User X does not even need to be an admin to do so.

Details

A user just needs to use the API endpoint: /api/chat/completions with their own API key (generated in OWUI) and the Chat ID of another user. OWUI does not check to match the Chat ID with the user that created that Chat ID. Note that both users will need access to the same model. This is especially relevant if there is a shared pipeline model between users.

PoC

Using OWUI v0.6.18
Sign in with any user X
Generate an API Key for user X using the settings
Create another user Y, and have a conversation in OWUI. Copy the Chat ID from the URL.
User X can now use the API /api/chat/completions and the Chat ID from step 4 to continue the conversation of user Y

Impact

Large impact to any user in OWUI. People can read your conversations, and access private information if they know your Chat ID (which is in the URL of the chat).

Resolution

Fixed in commit cf4218e68, first released in v0.9.0 (Apr 2026). The chat_completion handler at backend/open_webui/main.py:1868 now explicitly verifies chat ownership via Chats.is_chat_owner(chat_id, user.id) for any request that targets an existing chat, and raises 404 for non-owners (admin bypass preserved per the documented threat model). New chats (no chat_id supplied, or freshly inserted via the is_new_chat branch) are unaffected. Users on >= 0.9.0 are not affected.

Severity

7.1 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.8.12"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "open-webui"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.9.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-45349"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-639"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-14T20:24:35Z",
    "nvd_published_at": "2026-05-15T20:16:48Z",
    "severity": "HIGH"
  },
  "details": "### Summary\nAny user `X` can continue the conversation of any other user `Y`, as long as the Chat ID of `Y` is known. User `X` does not even need to be an admin to do so. \n\n### Details\nA user just needs to use the API endpoint: `/api/chat/completions` with their own API key (generated in OWUI) and the Chat ID of another user. **OWUI does not check to match the Chat ID with the user that created that Chat ID**. Note that both users will need access to the same model. This is especially relevant if there is a shared pipeline model between users. \n\n### PoC\n1. Using OWUI v0.6.18\n2. Sign in with any user `X`\n3. Generate an API Key for user `X` using the settings\n4. Create another user `Y`, and have a conversation in OWUI. Copy the Chat ID from the URL.\n5. User `X` can now use the API `/api/chat/completions` and the Chat ID from step 4 to continue the conversation of user `Y`\n\n### Impact\nLarge impact to any user in OWUI. People can read your conversations, and access private information if they know your Chat ID (which is in the URL of the chat). \n\n## Resolution\n\nFixed in commit [cf4218e68](https://github.com/open-webui/open-webui/commit/cf4218e688def6f11d195aeda6665ae5b5376b67), first released in **v0.9.0** (Apr 2026). The `chat_completion` handler at `backend/open_webui/main.py:1868` now explicitly verifies chat ownership via `Chats.is_chat_owner(chat_id, user.id)` for any request that targets an existing chat, and raises 404 for non-owners (admin bypass preserved per the documented threat model). New chats (no `chat_id` supplied, or freshly inserted via the `is_new_chat` branch) are unaffected. Users on `\u003e= 0.9.0` are not affected.",
  "id": "GHSA-gfm2-xm6c-37qc",
  "modified": "2026-05-15T23:54:00Z",
  "published": "2026-05-14T20:24:35Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/open-webui/open-webui/security/advisories/GHSA-gfm2-xm6c-37qc"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-45349"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-webui/open-webui/commit/cf4218e688def6f11d195aeda6665ae5b5376b67"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/open-webui/open-webui"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-webui/open-webui/releases/tag/v0.9.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Open WebUI has Broken Access Control for Completions API"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-45349 (GCVE-0-2026-45349)

FKIE_CVE-2026-45349

GHSA-GFM2-XM6C-37QC

Summary

Details

PoC

Impact

Resolution

Tags

Sightings

Nomenclature