CVE-2026-45387

When setting model permissions so that a group has read access to it, intending for other users to use it, those users also can read the model's system prompt.

However users may consider their system prompt confidential, so we consider this a security issue.

Compare https://genai.owasp.org/llmrisk/llm072025-system-prompt-leakage/ or prompt injections to get popular chatbots on the internet to reveal their prompt.

Details

We discovered that users can open the workspace model edit page /workspace/models/edit?id=notmymodel for models that do not appear in their workspace.

Saving is not possible, that permission check is correct.

On the API level:

• /api/v1/models/model?id=notmymodel -> returns the model details, most importantly params.system
• even though /api/v1/models/list does NOT contain the model since it checks for write permission.
• /api/models contains the model correctly and does not reveal the system prompt.

It seems inconsistent that the REST API list does not contain an item, but if you know the id, you can access it anyway.

PoC

• create model
• give read permission to group with another user
• other user can access /api/v1/models/model?id=notmymodel

System prommpt leakage

If this is intended behavior for the "read" permission, maybe there should be an additional "use" permission (which would be 99% of use cases of the read permission i believe).

CVE-2026-45387 has a CVSS score of 4.3 (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 (0.9.5); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-45387? CVE-2026-45387 is a medium-severity security vulnerability in open-webui (pip), affecting versions <= 0.9.4. It is fixed in 0.9.5.
2. How severe is CVE-2026-45387? CVE-2026-45387 has a CVSS score of 4.3 (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-2026-45387? open-webui (pip) versions <= 0.9.4 is affected.
4. Is there a fix for CVE-2026-45387? Yes. CVE-2026-45387 is fixed in 0.9.5. Upgrade to this version or later.
5. Is CVE-2026-45387 exploitable, and should I be worried? Whether CVE-2026-45387 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-2026-45387 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-2026-45387? Upgrade open-webui to 0.9.5 or later.