CVE-2026-44549 — open-webui
HIGHCVE-2026-44549 is a high-severity (CVSS 7.3) Cross-site Scripting (XSS) vulnerability in open-webui. A fix is available for open-webui — see the affected versions and patch details below.
Open WebUI: Stored XSS in excel file preview
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-2026-44549.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
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
Excel file attachments are previewed in an unsafe way. A crafted XLSX file payload can be used to cause the sheetjs function sheet_to_html to embed an XSS payload into the generated HTML. This is subsequently added to the DOM unsanitized via @html causing the payload to trigger.
Details
The function used to convert XLSX documents to HTML for preview does not perform any input validation or sanitisation for the generated HTML
https://github.com/open-webui/open-webui/blob/a7271532f8a38da46785afcaa7e65f9a45e7d753/src/lib/components/common/FileItemModal.svelte#L120-L133
XLSX attachments are processed by this function, converted to HTML with XLSX.utils.sheet_to_html before ultimately being assigned to the variable excelHtml. Later there is logic that causes this to be assigned directly to the DOM when the preview tab is selected.
https://github.com/open-webui/open-webui/blob/a7271532f8a38da46785afcaa7e65f9a45e7d753/src/lib/components/common/FileItemModal.svelte#L358-L400
PoC
A python script to generate a payload file is as follows:
import xlsxwriter
payload = '<img src=x onerror="alert(\'XSS Triggered by XLSX file\')">'
workbook = xlsxwriter.Workbook('xss_payload.xlsx')
worksheet = workbook.add_worksheet()
payload_format = workbook.add_format()
worksheet.write_rich_string('A1',
'This cell contains a hidden payload: ',
payload_format, payload
)
worksheet.write('A2', 'This is a safe cell.')
worksheet.write('B1', 'Column B')
workbook.close()
Upload the generated file as an attachment to a chat, open the file modal, and click preview. Observe the XSS triggers. <img width="2444" height="1386" alt="image" src="https://github.com/user-attachments/assets/8400efb0-ea6f-4878-abdb-4c2fe529241f" /> This same process can be triggered in shared chats, allowing the payload to be distributed to victims. <img width="2386" height="1646" alt="image" src="https://github.com/user-attachments/assets/d0eda49c-8fcf-4fc4-bbb0-c8951b0369c3" />
Impact
Any user can create a weaponised chat that can be shared and subsequently used to target other users.
Low privilege users are at risk of having their session taken over by a payload that reads their token from local storage and exfiltrates it to an attacker controlled server.
Admins are at risk of exposing the server to RCE via same chain described in GHSA-w7xj-8fx7-wfch.
Caveats
The file attachment in the shared chat must be opened and previewed to trigger the vulnerability.
Recommendation
Sanitise the generated HTML with DOMPurify before assigning it to the DOM.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | open-webui | all versions | 0.8.0pip install --upgrade 'open-webui==0.8.0' |
Affected Products
open webuiopenwebuiDetection & 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 0.8.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44549 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is CVE-2026-44549 in your dependencies?
Find it across PyPI, including transitive dependencies.