CVE-2021-21316 is a high-severity (CVSS 7.8) CWE-74 vulnerability in less-openui5. O3 Security confirms whether CVE-2021-21316 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Processing untrusted theming resources might execute arbitrary code (ACE)
Real-World Exposure
less-openui5Real-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
less-openui5 is an npm package which enables building OpenUI5 themes with Less.js. In less-openui5 before version 0.10., when processing theming resources (i.e. *.less files) with less-openui5 that originate from an untrusted source, those resources might contain JavaScript code which will be executed in the context of the build process. While this is a feature of the Less.js library it is an unexpected behavior in the context of OpenUI5 and SAPUI5 development. Especially in the context of UI5 Tooling which relies on less-openui5. An attacker might create a library or theme-library containing a custom control or theme, hiding malicious JavaScript code in one of the .less files. Refer to the referenced GHSA-3crj-w4f5-gwh4 for examples. Starting with Less.js version 3.0.0, the Inline JavaScript feature is disabled by default. less-openui5 however currently uses a fork of Less.js v1.6.3. Note that disabling the Inline JavaScript feature in Less.js versions 1.x, still evaluates code has additional double codes around it. We decided to remove the inline JavaScript evaluation feature completely from the code of our Less.js fork. This fix is available in less-openui5 version 0.10.0.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | less-openui5 | all versions | 0.10.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for less-openui5. 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 less-openui5 to 0.10.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21316 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-2021-21316 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-2021-21316. 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-2021-21316 in your dependencies?
O3 detects CVE-2021-21316 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.