CVE-2021-29438
MEDIUMCVE-2021-29438 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in @nextcloud/dialogs. O3 Security confirms whether CVE-2021-29438 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS) in @nextcloud/dialogs
Real-World Exposure
@nextcloud/dialogsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
The Nextcloud dialogs library (npm package @nextcloud/dialogs) before 3.1.2 insufficiently escaped text input passed to a toast. If your application displays toasts with user-supplied input, this could lead to a XSS vulnerability. The vulnerability has been patched in version 3.1.2 If you need to display HTML in the toast, explicitly pass the options.isHTML config flag.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @nextcloud/dialogs | all versions | 3.1.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @nextcloud/dialogs. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update @nextcloud/dialogs to 3.1.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-29438 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 pinpoints whether CVE-2021-29438 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2021-29438. 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-2021-29438 in your dependencies?
O3 detects CVE-2021-29438 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.