CVE-2026-33941
HighCVSS 8.2Exploitation Probability (EPSS)
Low risk21th percentile - higher than 21% of all known CVEs
Summary
A vulnerability in the Handlebars CLI precompiler (versions 4.0.0 through 4.7.8) allows arbitrary JavaScript injection via unsanitized template filenames and CLI arguments. An attacker can execute arbitrary code in Node.js or browser environments when the generated bundle is loaded.
Risk Assessment
The risk includes potential remote code execution (XSS/RCE) in build pipelines, leading to CI/CD compromise or sensitive data exfiltration.
Recommendation
Upgrade Handlebars to version 4.7.9 immediately. As workarounds, validate all CLI inputs, use trusted namespace strings from config files, and run the precompiler in a sandboxed environment (e.g., container).
Other vulnerabilities in Handlebars
See all- CVE-2026-33937Critical
A vulnerability in Handlebars versions 4.0.0 through 4.7.8 allows remote code execution (RCE) by injecting malicious JavaScript into generated code. The issue stems from unsanitized `value` fields in `NumberLiteral` AST nodes during template compilation. An attacker can supply a crafted AST object to `Handlebars.compile()`, leading to arbitrary code execution on the server.
- CVE-2026-33940High
A vulnerability in Handlebars versions 4.0.0 through 4.7.8 allows an attacker to achieve remote code execution on the server by injecting a crafted object into the template context. The object bypasses security checks in `resolvePartial()` and causes `env.compile()` to compile malicious JavaScript. The issue is fixed in version 4.7.9.
- CVE-2026-33939High
A vulnerability in Handlebars versions 4.0.0 through 4.7.8 causes a Node.js process crash when processing a template with an unregistered decorator. A TypeError occurs when the runtime attempts to invoke an undefined value as a function.
- CVE-2026-33938High
A vulnerability in Handlebars versions 4.0.0 through 4.7.8 allows arbitrary JavaScript execution on the server. The `@partial-block` special variable is stored in the template data context and can be overwritten by helpers that accept arbitrary objects. When a helper overwrites `@partial-block` with a crafted Handlebars AST, a subsequent `{{> @partial-block}}` invocation compiles and executes that AST, enabling code execution.
Original NVD description (English source)
Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, the Handlebars CLI precompiler (`bin/handlebars` / `lib/precompiler.js`) concatenates user-controlled strings — template file names and several CLI options — directly into the JavaScript it emits, without any escaping or sanitization. An attacker who can influence template filenames or CLI arguments can inject arbitrary JavaScript that executes when the generated bundle is loaded in Node.js or a browser. Version 4.7.9 fixes the issue. Some workarounds are available. First, validate all CLI inputs before invoking the precompiler. Reject filenames and option values that contain characters with JavaScript string-escaping significance (`"`, `'`, `;`, etc.). Second, use a fixed, trusted namespace string passed via a configuration file rather than command-line arguments in automated pipelines. Third, run the precompiler in a sandboxed environment (container with no write access to sensitive paths) to limit the impact of successful exploitation. Fourth, audit template filenames in any repository or package that is consumed by an automated build pipeline.