Handlebars.js <=4.7.8 Command Injection via CLI Precompiler
CVE-2026-33941 Published on March 27, 2026

Handlebars.js has JavaScript Injection in CLI Precompiler via Unescaped Names and Options
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.

NVD

Vulnerability Analysis

CVE-2026-33941 can be exploited with local system access, requires user interaction and a small amount of user privileges. This vulnerability is considered to have a low attack complexity. Public availability of a proof of concept (POC) exploit exists for CVE-2026-33941. The potential impact of an exploit of this vulnerability is considered to be very high.

Attack Vector:
LOCAL
Attack Complexity:
LOW
Privileges Required:
LOW
User Interaction:
REQUIRED
Scope:
CHANGED
Confidentiality Impact:
HIGH
Integrity Impact:
HIGH
Availability Impact:
HIGH

Weakness Types

What is a XSS Vulnerability?

The software does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

CVE-2026-33941 has been classified to as a XSS vulnerability or weakness.

What is a Code Injection Vulnerability?

The software constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.

CVE-2026-33941 has been classified to as a Code Injection vulnerability or weakness.

What is an Output Sanitization Vulnerability?

The software prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.

CVE-2026-33941 has been classified to as an Output Sanitization vulnerability or weakness.


Products Associated with CVE-2026-33941

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Red Hat Openshift Devspaces
 
Red Hat Logging
 
Red Hat Enterprise Linux (RHEL)
 
Red Hat Cryostat
 
Red Hat Jboss Data Grid
 
Red Hat Openshift Ai
 
Red Hat Jboss Enterprise Bpms Platform
 
Red Hat Cluster Observability Operator
 

Affected Versions

handlebars-lang handlebars.js: Red Hat Cluster Observability Operator 1.5.0: Red Hat OpenShift Dev Spaces 3.27: Logging Subsystem for Red Hat OpenShift: Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 9: Red Hat Cryostat 4: Red Hat Data Grid 8: Red Hat Enterprise Linux 7: Red Hat OpenShift AI (RHOAI): Red Hat Process Automation 7:

Exploit Probability

EPSS
0.29%
Percentile
20.76%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.