GHSA-h2cw-7qw9-56xr CVE-2026-45387 PYSEC-2026-2728
Open WebUI: Sharing models for others to use (read permission) also exposes model details (system prompt leakage)
- Severity
- 4.3 / 10
- Medium · CVSS 3.1
- Exploit chance (EPSS)
- 0.22%
- Chance of exploitation in the next 30 days. Higher than 12.55% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
- Fix
0.9.5- Upgrade open-webui to this version or later
Description
Summary
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/listdoes NOT contain the model since it checks for write permission. /api/modelscontains 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
Impact
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).
Affected versions
PyPI
| Package | Vulnerable | Fixed in |
|---|---|---|
| open-webui | < 0.9.5 |
0.9.5 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
open-webui PyPI → 0.9.5
- pip
pip install --upgrade "open-webui>=0.9.5"- poetry
poetry add "open-webui>=0.9.5"- uv
uv add "open-webui>=0.9.5"
Severity breakdown
CVSS 3.1 4.3
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
Weakness
CWE-200: Exposure of Sensitive Information to an Unauthorized Actor
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
How to prevent it
- Architecture and Design: Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
References
Advisories
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-wvm9-9g5j-623f Open WebUI: Users denied by the OAuth role policy can still sign in via token exchange | Medium | Also affects open-webui |
| GHSA-4qg5-cxx4-g927 Open WebUI: Users denied by the OAuth domain allowlist or role policy can still sign in via token exchange | Medium | Also affects open-webui |
| GHSA-jqhh-cjmq-vmv6 Open WebUI: Any authenticated user can hang the server via a cyclic chat message history | Medium | Also affects open-webui |
| GHSA-5x7x-4c3c-qf5w Open WebUI: Server-side fetches reach blocked and internal hosts via unvalidated HTTP redirect targets | Medium | Also affects open-webui |
| GHSA-3cgp-3cqx-j8w2 Open WebUI: Any authenticated user can hang the server via message deletion in a cyclic chat tree | Medium | Also affects open-webui |
| GHSA-34r3-9m95-vq73 Open WebUI: Any authenticated user can reach the Azure platform channel via server-side web fetch | High | Also affects open-webui |
| GHSA-2724-6cpj-gf3v Open WebUI: Non-admin users can delete admin-owned external knowledge connections via knowledge base deletion | High | Also affects open-webui |
| GHSA-3pf7-q2g3-wj28 Open WebUI: Any authenticated user can inject chats into another user's folder via chat completions | Medium | Also affects open-webui |
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