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-2026-33939
handlebars-lang handlebars.js — Handlebars.js has Denial of Service via Malformed Decorator Syntax in Template Compilation
AV AC PR UI S C I A CVSS EPSS %ile KEV
N L N N U N N H 7.5 .0076 53.6 —
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-2026-33939 (handlebars-lang handlebars.js). Public exploit reference added.
Sep 4 EXPLOIT PUBLISHED — CVE-2026-33939 (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, when a Handlebars template contains decorator syntax referencing an unregistered decorator (e.g. `{{*n}}`), the compiled template calls `lookupProperty(decorators, "n")`, which returns `undefined`. The runtime then immediately invokes the result as a function, causing an unhandled `TypeError: ... is not a function` that crashes the Node.js process. Any application that compiles user-supplied templates without wrapping the call in a `try/catch` is vulnerable to a single-request Denial of Service. Version 4.7.9 fixes the issue. Some workarounds are available. Wrap compilation and rendering in `try/catch`. Validate template input before passing it to `compile()`; reject templates containing decorator syntax (`{{*...}}`) if decorators are not used in your application. Use the pre-compilation workflow; compile templates at build time and serve only pre-compiled templates; do not call `compile()` at request time.
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-2026-33939 (handlebars-lang handlebars.js). Public exploit reference added. |
| September 4, 2026 | EXPLOIT PUBLISHED | EXPLOIT PUBLISHED — CVE-2026-33939 (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-2026-33939 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.
