CVE-2021-23567 is a high-severity (CVSS 7.5) CWE-835 vulnerability in colors. 4 public exploit references exist, so weaponization risk is real. O3 Security confirms whether CVE-2021-23567 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Infinite Loop in colors.js
Real-World Exposure
colorsReal-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 colors after 1.4.0 are vulnerable to Denial of Service (DoS) that was introduced through an infinite loop in the americanFlag module. Unfortunately this appears to have been a purposeful attempt by a maintainer of colors to make the package unusable, other maintainers' controls over this package appear to have been revoked in an attempt to prevent them from fixing the issue. Vulnerable Code js for (let i = 666; i < Infinity; i++;) { Alternative Remediation Suggested * Pin dependancy to 1.4.0
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | colors | ≥ 1.4.1 | No fix |
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 colors after 1.4.0 are vulnerable to Denial of Service (DoS)…
The package colors after 1.4.0 are vulnerable to Denial of Service (DoS)…
The package colors after 1.4.0 are vulnerable to Denial of Service (DoS)…
The package colors after 1.4.0 are vulnerable to Denial of Service (DoS)…
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for colors. 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.
Remediation status
No patched version of colors has shipped for CVE-2021-23567 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
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-2021-23567 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-2021-23567. 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-2021-23567 in your dependencies?
O3 detects CVE-2021-23567 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.