CVE-2021-23358
HIGHCVE-2021-23358 is a high-severity (CVSS 7.2) Code Injection vulnerability in underscore. 4 public exploit references exist, so weaponization risk is real. O3 Security confirms whether CVE-2021-23358 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Arbitrary Code Execution in underscore
Real-World Exposure
underscoreReal-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 package underscore from 1.13.0-0 and before 1.13.0-2, from 1.3.2 and before 1.12.1 are vulnerable to Arbitrary Code Injection via the template function, particularly when a variable property is passed as an argument as it is not sanitized.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | underscore | ≥ 1.3.2&&< 1.12.1 | 1.12.1 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
The package underscore from 1.13.0-0 and before 1.13.0-2, from 1.3.2 and…
The package underscore from 1.13.0-0 and before 1.13.0-2, from 1.3.2 and…
The package underscore from 1.13.0-0 and before 1.13.0-2, from 1.3.2 and…
The package underscore from 1.13.0-0 and before 1.13.0-2, from 1.3.2 and…
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for underscore. 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 underscore to 1.12.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-23358 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-2021-23358 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-2021-23358. 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-2021-23358 in your dependencies?
O3 detects CVE-2021-23358 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.