CVE-2026-106446
Description
A flaw was found in Handlebars. Incomplete validation of pre-parsed AST objects passed to compile() or precompile() allows unchecked AST fields to be emitted into generated JavaScript. An attacker who can supply an object instead of a template string can inject and execute arbitrary JavaScript in the application process.
Statement
This flaw has an Important impact. Exploitation requires an application to pass a non-string object (for example, a JSON-deserialized value) to Handlebars.compile() or Handlebars.precompile(). Applications that only pass template strings are not affected. When that unsafe calling pattern is present, injected JavaScript can run with the privileges of the Node.js process. The issue is not Critical for Red Hat scoring because successful exploitation depends on that non-default API usage condition (AC:H), not on typical string-template pipelines alone.
Mitigation
Upgrade to Handlebars 4.7.10 or later. Ensure only strings are passed to Handlebars.compile() and Handlebars.precompile(); reject non-string inputs. If templates are precompiled at build time, prefer the runtime-only build (handlebars/runtime) so compile() is unavailable on the server.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.1 | N/A | 9.8 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Access Control
Technical Impact: Bypass Protection Mechanism
In some cases, injectable code controls authentication; this may lead to a remote vulnerability.
Access Control
Technical Impact: Gain Privileges or Assume Identity
Injected code can access resources that the attacker is directly prevented from accessing.
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
When a product allows a user's input to contain code syntax, it might be possible for an attacker to craft the code in such a way that it will alter the intended control flow of the product. As a result, code injection can often result in the execution of arbitrary code. Code injection attacks can also lead to loss of data integrity in nearly all cases, since the control-plane data injected is always incidental to data recall or writing.
Non-Repudiation
Technical Impact: Hide Activities
Often the actions performed by injected control code are unlogged.
Frequently Asked Questions
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