CVE-2021-35440 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in smashing. O3 Security confirms whether CVE-2021-35440 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Smashing Cross-site Scripting vulnerability
Real-World Exposure
smashingReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
Smashing 1.3.4 is vulnerable to Cross Site Scripting (XSS). A URL for a widget can be crafted and used to execute JavaScript on the victim's computer. The JavaScript code can then steal data available in the session/cookies depending on the user environment (e.g. if re-using internal URL's for deploying, or cookies that are very permissive) private information may be retrieved by the attacker.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | smashing | all versions | 1.3.5 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for smashing. 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 smashing to 1.3.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-35440 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-2021-35440 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-2021-35440. 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-2021-35440 in your dependencies?
O3 detects CVE-2021-35440 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.