CVE-2026-33937
Description
A flaw was found in Handlebars. An attacker can exploit this by supplying a crafted Abstract Syntax Tree (AST) object to the Handlebars.compile() function. This allows the injection and execution of arbitrary JavaScript code due to improper sanitization of the value field in NumberLiteral AST nodes. This vulnerability can lead to Remote Code Execution (RCE) on the server.
Statement
This is an Important vulnerability in Handlebars that allows for Remote Code Execution. The flaw occurs when the Handlebars.compile() function processes a specially crafted Abstract Syntax Tree (AST) object, leading to the injection and execution of arbitrary JavaScript code. Red Hat products utilizing Handlebars are affected if they process untrusted input through the compile() function.
Mitigation
To mitigate this issue, ensure that any input provided to the `Handlebars.compile()` function is strictly validated to be a string type, preventing the injection of crafted Abstract Syntax Tree (AST) objects. Additionally, for deployments where templates are pre-compiled at build time, consider utilizing the Handlebars runtime-only build (`handlebars/runtime`). This build variant does not include the `compile()` function, thereby eliminating the attack vector. If the application is a service, a restart may be required for the changes to take effect.
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).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 9.8 | N/A | 9.8 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | 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:L/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.
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