GHSA-2cf5-4w76-r9qv
HIGHGHSA-2cf5-4w76-r9qv is a high-severity (CVSS 7.3) remote code execution vulnerability in handlebars. O3 Security confirms whether GHSA-2cf5-4w76-r9qv is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Arbitrary Code Execution in handlebars
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
handlebarsnpmDescription
Versions of handlebars prior to 3.0.8 or 4.5.2 are vulnerable to Arbitrary Code Execution. The package's lookup helper fails to properly validate templates, allowing attackers to submit templates that execute arbitrary JavaScript in the system. It can be used to run arbitrary code in a server processing Handlebars templates or on a victim's browser (effectively serving as Cross-Site Scripting).
The following template can be used to demonstrate the vulnerability:
{{#with split as |a|}}
{{pop (push "alert('Vulnerable Handlebars JS');")}}
{{#with (concat (lookup join (slice 0 1)))}}
{{#each (slice 2 3)}}
{{#with (apply 0 a)}}
{{.}}
{{/with}}
{{/each}}
{{/with}}
{{/with}}
{{/with}}```
## Recommendation
Upgrade to version 3.0.8, 4.5.2 or later.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | handlebars | all versions | 3.0.8 |
| 📦npm | handlebars | ≥ 4.0.0&&< 4.5.2 | 4.5.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for handlebars. 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 handlebars to 3.0.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-2cf5-4w76-r9qv 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 GHSA-2cf5-4w76-r9qv 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 GHSA-2cf5-4w76-r9qv. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-2cf5-4w76-r9qv in your dependencies?
O3 detects GHSA-2cf5-4w76-r9qv across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.