Summary
Open WebUI: Any authenticated user can cancel another user's chat generation via the chat delete endpoint
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.
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 sendDELETE /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.
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.
The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.
CVE-2026-70483 has a CVSS score of 3.1 (Low). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.11.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
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.
Frequently Asked Questions
- What is CVE-2026-70483? CVE-2026-70483 is a low-severity missing authorization vulnerability in open-webui (pip), affecting versions >= 0.9.6, < 0.11.0. It is fixed in 0.11.0. The application does not perform an authorization check before performing a sensitive operation.
- How severe is CVE-2026-70483? CVE-2026-70483 has a CVSS score of 3.1 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of open-webui are affected by CVE-2026-70483? open-webui (pip) versions >= 0.9.6, < 0.11.0 is affected.
- Is there a fix for CVE-2026-70483? Yes. CVE-2026-70483 is fixed in 0.11.0. Upgrade to this version or later.
- Is CVE-2026-70483 exploitable, and should I be worried? Whether CVE-2026-70483 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-70483 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-70483? Upgrade
open-webuito 0.11.0 or later.