CVE-2026-45349

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

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

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.

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).

CVE-2026-45349 has a CVSS score of 7.1 (High). 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 (0.9.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-45349? CVE-2026-45349 is a high-severity security vulnerability in open-webui (pip), affecting versions <= 0.8.12. It is fixed in 0.9.0.
2. How severe is CVE-2026-45349? CVE-2026-45349 has a CVSS score of 7.1 (High). 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-2026-45349? open-webui (pip) versions <= 0.8.12 is affected.
4. Is there a fix for CVE-2026-45349? Yes. CVE-2026-45349 is fixed in 0.9.0. Upgrade to this version or later.
5. Is CVE-2026-45349 exploitable, and should I be worried? Whether CVE-2026-45349 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-2026-45349 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-2026-45349? Upgrade open-webui to 0.9.0 or later.