CVE-2026-33940
Description
A flaw was found in Handlebars.js. A remote attacker can exploit this vulnerability by providing a specially crafted object within the template context. This crafted object, when processed by a dynamic partial lookup, can bypass security checks and be interpreted as malicious code. This allows the attacker to execute arbitrary commands on the server where Handlebars.js is running.
Statement
This is an Important arbitrary code execution vulnerability in Handlebars.js. The flaw can be exploited when an application uses Handlebars.js with dynamic partial lookups and processes user-controlled data within the template context. Red Hat products bundling Handlebars.js are affected if they meet these specific conditions for exploitation.
Mitigation
To mitigate this issue, use the runtime-only build of Handlebars.js, which prevents the fallback compilation path from being reached. Alternatively, sanitize all context data before rendering to ensure no non-primitive objects are passed to dynamic partials. Avoid dynamic partial lookups (`{{> (lookup ...)}}`) when context data is user-controlled. Implementing these mitigations may require application-level changes.
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 | 8.1 | N/A | 8.1 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| 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:H/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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