CVE-2026-33940

Status: ModifiedHigh (8.1)—

Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, a crafted object placed in the template context can bypass all conditional guards in `resolvePartial()` and cause `invokePartial()` to return `undefined`. The Handlebars runtime then treats the unresolved partial as a source that needs to be compiled, passing the crafted object to `env.compile()`. Because the object is a valid Handlebars AST containing injected code, the generated JavaScript executes arbitrary commands on the server.

Read full descriptionShow less

The attack requires the adversary to control a value that can be returned by a dynamic partial lookup. Version 4.7.9 fixes the issue. Some workarounds are available. First, use the runtime-only build (`require('handlebars/runtime')`). Without `compile()`, the fallback compilation path in `invokePartial` is unreachable. Second, sanitize context data before rendering: Ensure no value in the context is a non-primitive object that could be passed to a dynamic partial. Third, avoid dynamic partial lookups (`{{> (lookup ...)}}`) when context data is user-controlled.

CVSS

Version: 3.1
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Base score: 8.1

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 0.79%
Percentile among all scored CVEs: 55
Score date: 10/5/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

ExploitationT1190 Exploit Public-Facing Applicationinitial access85 %
Primary impactT1059 Command and Scripting Interpreterexecution90 %
Secondary impactT1565.001 Stored Data Manipulationimpact65 %

Vulnerabilidad de inyección de código (CWE-94) en aplicación web Handlebars expuesta en red. Atacante controla contexto de plantilla para inyectar AST malicioso que se compila y ejecuta arbitrariamente en el servidor, permitiendo ejecución de comandos.

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

Privileged Account Management Vulnerability Scanning Restrict Web-Based Content Restrict File and Directory Permissions Remote Data Storage Network Segmentation

Affected technologies (1)

Handlebarsjs — Handlebars

CWEs

CWE-94, CWE-843
CWE-94

References

Raw JSON (NVD)

Show

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