Description
Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, a crafted object placed in the template context can bypass all conditional guards in `resolvePartial()` and cause `invokePartial()` to return `undefined`. The Handlebars runtime then treats the unresolved partial as a source that needs to be compiled, passing the crafted object to `env.compile()`. Because the object is a valid Handlebars AST containing injected code, the generated JavaScript executes arbitrary commands on the server. The attack requires the adversary to control a value that can be returned by a dynamic partial lookup. Version 4.7.9 fixes the issue. Some workarounds are available. First, use the runtime-only build (`require('handlebars/runtime')`). Without `compile()`, the fallback compilation path in `invokePartial` is unreachable. Second, sanitize context data before rendering: Ensure no value in the context is a non-primitive object that could be passed to a dynamic partial. Third, avoid dynamic partial lookups (`{{> (lookup ...)}}`) when context data is user-controlled.
Analysis
No analysis available yet.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| handlebars-lang | handlebars.js | affected |
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Remediation
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Tracking
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Advisories
| Source | ID | Title |
|---|---|---|
 Github GHSA |
GHSA-xhpv-hc6g-r9c6 | Handlebars.js has JavaScript Injection via AST Type Confusion when passing an object as dynamic partial |
References
History
Sat, 28 Mar 2026 03:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, a crafted object placed in the template context can bypass all conditional guards in `resolvePartial()` and cause `invokePartial()` to return `undefined`. The Handlebars runtime then treats the unresolved partial as a source that needs to be compiled, passing the crafted object to `env.compile()`. Because the object is a valid Handlebars AST containing injected code, the generated JavaScript executes arbitrary commands on the server. The attack requires the adversary to control a value that can be returned by a dynamic partial lookup. Version 4.7.9 fixes the issue. Some workarounds are available. First, use the runtime-only build (`require('handlebars/runtime')`). Without `compile()`, the fallback compilation path in `invokePartial` is unreachable. Second, sanitize context data before rendering: Ensure no value in the context is a non-primitive object that could be passed to a dynamic partial. Third, avoid dynamic partial lookups (`{{> (lookup ...)}}`) when context data is user-controlled. | |
| Title | Handlebars.js has JavaScript Injection via AST Type Confusion when passing an object as dynamic partial | |
| Weaknesses | CWE-843 CWE-94 |
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| Metrics |
cvssV3_1
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Subscriptions
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MITRE
Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-03-27T21:11:10.719Z
Reserved: 2026-03-24T19:50:52.103Z
Link: CVE-2026-33940
Vulnrichment
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NVD
Status : Received
Published: 2026-03-27T22:16:21.030
Modified: 2026-03-27T22:16:21.030
Link: CVE-2026-33940
Redhat
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OpenCVE Enrichment
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