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-2026-33938
handlebars-lang handlebars.js — Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block
AV AC PR UI S C I A CVSS EPSS %ile KEV
N H N N U H H H 8.1 .0084 56.5 —
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)
Aug 31 EXPLOIT PUBLISHED — CVE-2026-33938 (handlebars-lang handlebars.js). Public exploit reference added.
Sep 4 EXPLOIT PUBLISHED — CVE-2026-33938 (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, the `@partial-block` special variable is stored in the template data context and is reachable and mutable from within a template via helpers that accept arbitrary objects. When a helper overwrites `@partial-block` with a crafted Handlebars AST, a subsequent invocation of `{{> @partial-block}}` compiles and executes that AST, enabling arbitrary JavaScript execution on the server. Version 4.7.9 fixes the issue. Some workarounds are available. First, use the runtime-only build (`require('handlebars/runtime')`). The `compile()` method is absent, eliminating the vulnerable fallback path. Second, audit registered helpers for any that write arbitrary values to context objects. Helpers should treat context data as read-only. Third, avoid registering helpers from third-party packages (such as `handlebars-helpers`) in contexts where templates or context data can be influenced by untrusted input.
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) |
| August 31, 2026 | EXPLOIT PUBLISHED | EXPLOIT PUBLISHED — CVE-2026-33938 (handlebars-lang handlebars.js). Public exploit reference added. |
| September 4, 2026 | EXPLOIT PUBLISHED | EXPLOIT PUBLISHED — CVE-2026-33938 (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-2026-33938 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.
