Code Injection in handlebars.js - CVE-2026-33938
Published: April 2, 2026
Vulnerability identifier: #VU124841
CSH Severity: High
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
CVE-ID: CVE-2026-33938
CWE-ID: CWE-94
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: The Handlebars Templating Language
Affected software:
handlebars.js
handlebars.js
Detailed vulnerability description
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to code injection through type confusion in the @partial-block handling and dynamic compilation fallback when processing a tampered @partial-block value during partial invocation. A remote attacker can overwrite @partial-block with a crafted Handlebars AST to execute arbitrary code.
The issue affects handlebars.js when templates can reach and mutate the data frame, and a subsequent {{> @partial-block}} causes the crafted AST to be compiled and executed in the server process.
How to mitigate CVE-2026-33938
Install security update from vendor's website.