Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.
CVE-2026-33940
handlebars-lang handlebars.js — Handlebars.js has JavaScript Injection via AST Type Confusion when passing an object as dynamic partial
AV AC PR UI S C I A CVSS EPSS %ile KEV
N H N N U H H H 8.1 .0079 54.8 —
AFFECTED
Product Versions Fixed
handlebars.js >= 4.0.0, < 4.7.9 – —
TIMELINE
Mar 24 Reserved by GitHub_M
Mar 27 Published (CNA: GitHub_M)
Sep 1 EXPLOIT PUBLISHED — CVE-2026-33940 (handlebars-lang handlebars.js). Public exploit reference added.
Sep 4 EXPLOIT PUBLISHED — CVE-2026-33940 (handlebars-lang handlebars.js). Public exploit reference 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.
Lifecycle
Complete event history — 4 events, chronological
| Date | Event | Detail |
|---|
| March 24, 2026 | Reserved | Reserved by GitHub_M |
| March 27, 2026 | Published | Published (CNA: GitHub_M) |
| September 1, 2026 | EXPLOIT PUBLISHED | EXPLOIT PUBLISHED — CVE-2026-33940 (handlebars-lang handlebars.js). Public exploit reference added. |
| September 4, 2026 | EXPLOIT PUBLISHED | EXPLOIT PUBLISHED — CVE-2026-33940 (handlebars-lang handlebars.js). Public exploit reference added. |
Affected
Affected products and packages — 1 row
| Vendor | Product / Package | Ecosystem | Version introduced | Fixed |
|---|
| handlebars-lang | handlebars.js | — | >= 4.0.0, < 4.7.9 | — |
About this page
This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-33940 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Sunday, October 4, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.
