GHSA-mhpg-c27v-6mxr — nicegui
HIGHGHSA-mhpg-c27v-6mxr is a high-severity (CVSS 7.2) Cross-site Scripting (XSS) vulnerability in nicegui. A fix is available for nicegui — see the affected versions and patch details below.
NiceGUI apps which use `ui.sub_pages` vulnerable to zero-click XSS
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.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for GHSA-mhpg-c27v-6mxr.
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
GHSA-mhpg-c27v-6mxr 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 377,166 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
niceguiReal-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 unsafe implementation in the pushstate event listener used by ui.sub_pages allows an attacker to manipulate the fragment identifier of the URL, which they can do despite being cross-site, using an iframe.
Details
The problem is traced as follows:
- On
pushstate,handleStateEventis executed.
handleStateEventemitssub_pages_openevent.
SubPagesRouter(used byui.sub_pages), lisnening onsub_pages_open,_handle_openruns.
_handle_openfinds anySubPagesand runs_show()on them
- If the if-logic is followed or debug prints are added, it can be found that it calls
self._handle_scrolling(match, behavior='smooth')directly
- CULPRIT
_handle_scrollingruns_scroll_to_fragmentas there is a fragment, which runs vulnerable JS if thefragment(attacker-controlled) escapes out of the quotes.
PoC
Just visiting this page (no click required), consistently triggers XSS in https://nicegui.io domain.
<html>
<body>
<iframe id="myiframe" src="https://nicegui.io" width="100%" height="600px" onload="triggerXSS()"></iframe>
<script>
function triggerXSS() {
if (!myiframe.src.includes("#")) {
myiframe.src = "https://nicegui.io#x');alert(document.domain)//";
}
}
</script>
</body>
</html>
Impact
Any page which uses ui.sub_pages and does not actively prevent itself from being put in an iframe is affected.
The impact is high since by-default NiceGUI pages are iframe-embeddable with no native opt-out functionalities except by manipulating the underlying app via FastAPI methods, and that ui.sub_pages is actively promoted as the new modern way to create Single-Page Applications (SPA).
Patch
- Not use
ui.sub_pages - Block iframe with the following code
@app.middleware('http')
async def iframe_blocking_middleware(request, call_next):
response = await call_next(request)
response.headers['X-Frame-Options'] = 'DENY'
return response
Appendix
AI is used safely to judge the CVSS scoring (input is censored).
Please find the results in https://poe.com/s/3FXuwp7TAYxqLomARXma
Scoring update after manual review
The scoring done by AI was quite biased. Upon further review it is less dramatic.
- User Interaction None: There's almost no interaction required, and none of the interaction is with the vulnerable system.
- Confidentiality & Integrity Low: The extent of data confidentiality & integrity loss is bounded by the highest priviledged user in the entire NiceGUI application. There does not exist a means of performing data manipulating tasks that said admin cannot already do.
- Availability None: No DDoS is possible with this. Site remains performant as ever.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | nicegui | ≥ 2.22.0&&< 3.5.0 | 3.5.0pip install --upgrade 'nicegui==3.5.0' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nicegui, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update nicegui to 3.5.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mhpg-c27v-6mxr 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 GHSA-mhpg-c27v-6mxr can be triaged on real exposure rather than presence alone.
Tailored to GHSA-mhpg-c27v-6mxr. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-mhpg-c27v-6mxr in your dependencies?
O3 Security finds GHSA-mhpg-c27v-6mxr across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.