How severe is CVE-2018-6333?

CVE-2018-6333 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2018-6333?

CVE-2018-6333 affects the following packages: nuclide (npm). Ecosystems affected: npm.

How do I fix CVE-2018-6333?

Update nuclide to 0.290.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2018-6333 is resolved across your whole dependency graph.

How do I detect CVE-2018-6333 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nuclide. 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.

How do I mitigate CVE-2018-6333 if there is no patch (or I can't update yet)?

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 does O3 Security protect against CVE-2018-6333?

O3 pinpoints whether CVE-2018-6333 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2018-6333 actively exploited in the wild?

No public exploit code has been indexed for CVE-2018-6333 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2018-6333?

CVE-2018-6333 has an EPSS (Exploit Prediction Scoring System) score of 2.3%, placing it in the 81th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

When was CVE-2018-6333 published, and has it been updated?

CVE-2018-6333 was published on December 31, 2018 and was last updated on March 14, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2018-6333: Nuclide Improper Input Validation (Critical 9.8)

EPSS Exploitation Probability

via FIRST.org ↗

2.3%probability of exploitation in next 30 days

Lower Risk81th percentile+1.22%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

1 pkg affected

Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.

nuclidenpm

408downloads / week

Description

The hhvm-attach deep link handler in Nuclide did not properly sanitize the provided hostname parameter when rendering. As a result, a malicious URL could be used to render HTML and other content inside of the editor's context, which could potentially be chained to lead to code execution. This issue affected Nuclide prior to v0.290.0.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`nuclide`	all versions	0.290.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nuclide. 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 nuclide to 0.290.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2018-6333 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-2018-6333 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-2018-6333. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

The hhvm-attach deep link handler in Nuclide did not properly sanitize the provided hostname parameter when rendering. As a result, a malicious URL could be used to render HTML and other content inside of the editor's context, which could potentially be chained to lead to code execution. This issue affected Nuclide prior to v0.290.0.

O3 Security · Impact-Aware SCA

Is CVE-2018-6333 in your dependencies?

O3 detects CVE-2018-6333 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works

CVE-2018-6333