Vulnerability-Lookup

CVE-2026-70483 (GCVE-0-2026-70483)

Vulnerability from cvelistv5 – Published: 2026-08-04 19:54 – Updated: 2026-08-05 19:03

Title

Open WebUI: Any authenticated user can cancel another user's chat generation via the chat delete endpoint

Summary

Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.9.6 until 0.11.0, DELETE /api/v1/chats/{id} cancelled a chat's in-flight tasks before checking whether the caller could delete that chat. Any authenticated user who knew another user's chat id could abort that user's running model response, title generation, or tag generation, even though the delete was refused and no chat data was deleted, modified, or disclosed. This issue is fixed in 0.11.0.

Severity

3.1 (Low)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-862 - Missing Authorization

Assigner

GitHub_M

References

4 references

URL	Tags
https://github.com/open-webui/open-webui/security…	x_refsource_CONFIRM
https://github.com/open-webui/open-webui/pull/27006	x_refsource_MISC
https://github.com/open-webui/open-webui/commit/4…	x_refsource_MISC
https://github.com/open-webui/open-webui/releases…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
open-webui	open-webui	Affected: >= 0.9.6, < 0.11.0

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GHSA-3VF6-64VR-3G56

Vulnerability from github – Published: 2026-08-04 19:54 – Updated: 2026-08-04 19:54

Summary

Open WebUI: Any authenticated user can cancel another user's chat generation via the chat delete endpoint

Details

Summary

DELETE /api/v1/chats/{id} cancelled a chat's in-flight tasks before it checked whether the caller was allowed to delete that chat. Any authenticated user who knew another user's chat id could therefore abort that user's running model response, title generation or tag generation. The deletion itself was still refused, so the only missing control was on the cancellation side effect.

Preconditions

Default configuration, no special deployment shape. The attacker needs a normal account with the default user role and nothing else: the chat.delete permission is not required, and revoking it does not prevent the cancellation. The attacker also needs the victim's chat id, which is returned by the read-only shared-chat endpoint when a chat or a folder has been shared with them - otherwise enumerating the chat id requires guessing the chat id or brute forcing it, and the victim must have a generation running at that moment.

Impact

A user can repeatedly interrupt another user's generations without any write access to the target chat. Nothing is deleted, modified or disclosed, and the victim can simply regenerate, so the effect is limited to availability of in-flight responses. Because the attacker only needs a chat id, the interruption can be scripted and repeated for as long as the id stays valid.

Fix

Fixed in https://github.com/open-webui/open-webui/pull/27006, released in 0.11.0. The handler now resolves and authorizes the chat first and only cancels tasks and deletes once the caller is an admin or a permitted owner; an unauthorized caller gets 401 or 404 with no cancellation.

Root cause

Affected component: delete_chat_by_id in backend/open_webui/routers/chats.py, serving DELETE /api/v1/chats/{id}. Affected setup: every build from 0.9.6 up to and including 0.10.2.

The cancellation was written as a cleanup step for the delete that follows it, and it was placed at the top of the handler so that it would run before the chat row disappeared. That put an unauthenticated-by-ownership side effect ahead of every check in the function: the admin branch, the chat.delete permission check, and the owner lookup all ran afterwards, so their outcome could no longer affect whether the tasks were stopped. The dedicated task-stop endpoint already verified ownership before calling the same helper, so the intended ordering existed elsewhere in the codebase.

Proof of concept

Against a 0.10.2 instance with two accounts, a victim admin and an attacker holding the default user role, and an upstream that streams slowly:

As the victim, start a generation in a chat and confirm GET /api/tasks/chat/{chat_id} reports one active task.
As the attacker, confirm GET /api/v1/chats/{chat_id} returns 401, then send DELETE /api/v1/chats/{chat_id}.
The delete is refused with 404, the chat still exists, but the victim's task list is now empty and the assistant message is marked done mid-generation. A control run without step 2 keeps generating.

Repeating step 2 with the chat.delete permission revoked for the user role returns 401 and still cancels the task. The same sequence against 0.11.0 leaves the task running.

Credits

@GabrielGomesAL, who reported the missing authorization on the chat delete endpoint.

Severity

3.1 (Low)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "open-webui"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.9.6"
            },
            {
              "fixed": "0.11.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-70483"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-862"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-04T19:54:49Z",
    "nvd_published_at": null,
    "severity": "LOW"
  },
  "details": "## Summary\n`DELETE /api/v1/chats/{id}` cancelled a chat\u0027s in-flight tasks before it checked whether the caller was allowed to delete that chat. Any authenticated user who knew another user\u0027s chat id could therefore abort that user\u0027s running model response, title generation or tag generation. The deletion itself was still refused, so the only missing control was on the cancellation side effect.\n\n## Preconditions\nDefault configuration, no special deployment shape. The attacker needs a normal account with the default `user` role and nothing else: the `chat.delete` permission is not required, and revoking it does not prevent the cancellation. The attacker also needs the victim\u0027s chat id, which is returned by the read-only shared-chat endpoint when a chat or a folder has been shared with them - otherwise enumerating the chat id requires guessing the chat id or brute forcing it, and the victim must have a generation running at that moment.\n\n## Impact\nA user can repeatedly interrupt another user\u0027s generations without any write access to the target chat. Nothing is deleted, modified or disclosed, and the victim can simply regenerate, so the effect is limited to availability of in-flight responses. Because the attacker only needs a chat id, the interruption can be scripted and repeated for as long as the id stays valid.\n\n## Fix\nFixed in https://github.com/open-webui/open-webui/pull/27006, released in 0.11.0. The handler now resolves and authorizes the chat first and only cancels tasks and deletes once the caller is an admin or a permitted owner; an unauthorized caller gets 401 or 404 with no cancellation.\n\n## Root cause\nAffected component: `delete_chat_by_id` in `backend/open_webui/routers/chats.py`, serving `DELETE /api/v1/chats/{id}`. Affected setup: every build from 0.9.6 up to and including 0.10.2.\n\nThe cancellation was written as a cleanup step for the delete that follows it, and it was placed at the top of the handler so that it would run before the chat row disappeared. That put an unauthenticated-by-ownership side effect ahead of every check in the function: the admin branch, the `chat.delete` permission check, and the owner lookup all ran afterwards, so their outcome could no longer affect whether the tasks were stopped. The dedicated task-stop endpoint already verified ownership before calling the same helper, so the intended ordering existed elsewhere in the codebase.\n\n## Proof of concept\nAgainst a 0.10.2 instance with two accounts, a victim admin and an attacker holding the default `user` role, and an upstream that streams slowly:\n\n1. As the victim, start a generation in a chat and confirm `GET /api/tasks/chat/{chat_id}` reports one active task.\n2. As the attacker, confirm `GET /api/v1/chats/{chat_id}` returns 401, then send `DELETE /api/v1/chats/{chat_id}`.\n3. The delete is refused with 404, the chat still exists, but the victim\u0027s task list is now empty and the assistant message is marked done mid-generation. A control run without step 2 keeps generating.\n\nRepeating step 2 with the `chat.delete` permission revoked for the `user` role returns 401 and still cancels the task. The same sequence against 0.11.0 leaves the task running.\n\n## Credits\n@GabrielGomesAL, who reported the missing authorization on the chat delete endpoint.",
  "id": "GHSA-3vf6-64vr-3g56",
  "modified": "2026-08-04T19:54:49Z",
  "published": "2026-08-04T19:54:49Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/open-webui/open-webui/security/advisories/GHSA-3vf6-64vr-3g56"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-webui/open-webui/pull/27006"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-webui/open-webui/commit/4f93c3e36c1734342a32c312bdb0516c66d8e93c"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/open-webui/open-webui"
    },
    {
      "type": "WEB",
      "url": "https://github.com/open-webui/open-webui/releases/tag/v0.11.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Open WebUI: Any authenticated user can cancel another user\u0027s chat generation via the chat delete endpoint"
}

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

CVE-2026-70483 (GCVE-0-2026-70483)

GHSA-3VF6-64VR-3G56

Summary

Preconditions

Impact

Fix

Root cause

Proof of concept

Credits

Tags

Sightings

Nomenclature