CVE-2026-25526

JinJava is a Java-based template engine based on django template syntax, adapted to render jinja templates. Prior to versions 2.7.6 and 2.8.3, JinJava is vulnerable to arbitrary Java execution via bypass through ForTag. This allows arbitrary Java class instantiation and file access bypassing built-in sandbox restrictions. This issue has been patched in versions 2.7.6 and 2.8.3.

JinJava is a Java-based template engine based on django template syntax, adapted to render jinja templates. Prior to versions 2.7.6 and 2.8.3, JinJava is vulnerable to arbitrary Java execution via bypass through ForTag. This allows arbitrary Java class instantiation and file access bypassing built-in sandbox restrictions. This issue has been patched in versions 2.7.6 and 2.8.3.

## Impact **Vulnerability Type**: Sandbox Bypass / Remote Code Execution **Affected Component**: Jinjava **Affected Users**: - Organizations using HubSpot's Jinjava template rendering engine for user-provided template content - Any system that renders untrusted Jinja templates using HubSpot's Jinjava implementation - Users with the ability to create or edit custom code templates **Severity**: **Critical** - allows arbitrary Java class instantiation and file access bypassing built-in sandbox restrictions **Root Cause**: Multiple security bypass vulnerabilities in Jinjava's sandbox mechanism: 1. **ForTag Property Access Bypass**: The `ForTag` class does not enforce `JinjavaBeanELResolver` restrictions when iterating over object properties using `Introspector.getBeanInfo()` and invoking getter methods via `PropertyDescriptor.getReadMethod()` 2. **Restricted Class Instantiation**: The sandbox's type allowlist can be bypassed by using ObjectMapper to instantiate classes through JSON deserialization, including creating new `JinjavaELContext` and `JinjavaConfig` instances **Attack Vector**: An attacker with the ability to create or edit Jinja templates can: - Access arbitrary getter methods on objects in the template context - Instantiate `ObjectMapper` to enable default typing - Create arbitrary Java classes by bypassing type allowlists - Read files from the server filesystem (demonstrated with `/etc/passwd`) - Potentially execute arbitrary code ## Patches **Status**: Patched - CVE-2026-25526 Users should upgrade to one of the following versions which contain fixes for this vulnerability: - **JinJava 2.8.3** or later - **JinJava 2.7.6** or later **Fix Components**: 1. **ForTag Security Hardening** - Added security checks to `ForTag.renderForCollection()` to enforce `JinjavaBeanELResolver` restrictions - Implemented property access validation against restricted properties/methods before invoking getter methods - Added checks for restricted class types before introspection 2. **Enhanced Type Validation** - Improved validation in `JinjavaBeanELResolver.isRestrictedClass()` to prevent instantiation of sensitive types - Added additional restricted types to the denylist - Implemented deeper validation for types created via ObjectMapper deserialization 3. **Configuration Protection** - Added checks to prevent creation of new `JinjavaConfig` or `JinjavaELContext` instances via ObjectMapper - Prevented modification of `readOnlyResolver` configuration from untrusted templates - Implemented additional safeguards around ELResolver configuration 4. **Collection Type Validation** - Implemented proper type validation in `HubLELResolver` to prevent collection type wrapping bypasses - Added checks for wrapped types in collection deserialization - Implemented validation for all types within collections against allowlists 5. **ObjectMapper Restrictions** - Added additional restrictions on `ObjectMapper.enableDefaultTyping()` to prevent enabling via less restrictive ELResolver - Ensured default typing cannot be enabled without proper authorization **Information for Users**: Upgrade to version 2.8.3 or 2.7.6 or later to address this vulnerability. ## References ### Project Resources - **Jinjava Source Code**: [github.com/HubSpot/jinjava](https://github.com/HubSpot/jinjava) - **Jinjava Releases**: [github.com/HubSpot/jinjava/releases](https://github.com/HubSpot/jinjava/releases) ### Security Standards & Classifications - **CWE-502**: Deserialization of Untrusted Data - **CWE-913**: Improper Control of Dynamically-Managed Code Resources - **CWE-94**: Improper Control of Generation of Code ('Code Injection') - **CVSS v3.1**: Common Vulnerability Scoring System ### Additional Resources - [OWASP Template Injection](https://owasp.org/www-community/attacks/Server_Side_Template_Injection) - [Java Deserialization Security](https://cheatsheetseries.owasp.org/cheatsheets/Deserialization_Cheat_Sheet.html) - [CVE Standards and Procedures](https://cve.mitre.org/)

## Impact **Vulnerability Type**: Sandbox Bypass / Remote Code Execution **Affected Component**: Jinjava **Affected Users**: - Organizations using HubSpot's Jinjava template rendering engine for user-provided template content - Any system that renders untrusted Jinja templates using HubSpot's Jinjava implementation - Users with the ability to create or edit custom code templates **Severity**: **Critical** - allows arbitrary Java class instantiation and file access bypassing built-in sandbox restrictions **Root Cause**: Multiple security bypass vulnerabilities in Jinjava's sandbox mechanism: 1. **ForTag Property Access Bypass**: The `ForTag` class does not enforce `JinjavaBeanELResolver` restrictions when iterating over object properties using `Introspector.getBeanInfo()` and invoking getter methods via `PropertyDescriptor.getReadMethod()` 2. **Restricted Class Instantiation**: The sandbox's type allowlist can be bypassed by using ObjectMapper to instantiate classes through JSON deserialization, including creating new `JinjavaELContext` and `JinjavaConfig` instances **Attack Vector**: An attacker with the ability to create or edit Jinja templates can: - Access arbitrary getter methods on objects in the template context - Instantiate `ObjectMapper` to enable default typing - Create arbitrary Java classes by bypassing type allowlists - Read files from the server filesystem (demonstrated with `/etc/passwd`) - Potentially execute arbitrary code ## Patches **Status**: Patched - CVE-2026-25526 Users should upgrade to one of the following versions which contain fixes for this vulnerability: - **JinJava 2.8.3** or later - **JinJava 2.7.6** or later **Fix Components**: 1. **ForTag Security Hardening** - Added security checks to `ForTag.renderForCollection()` to enforce `JinjavaBeanELResolver` restrictions - Implemented property access validation against restricted properties/methods before invoking getter methods - Added checks for restricted class types before introspection 2. **Enhanced Type Validation** - Improved validation in `JinjavaBeanELResolver.isRestrictedClass()` to prevent instantiation of sensitive types - Added additional restricted types to the denylist - Implemented deeper validation for types created via ObjectMapper deserialization 3. **Configuration Protection** - Added checks to prevent creation of new `JinjavaConfig` or `JinjavaELContext` instances via ObjectMapper - Prevented modification of `readOnlyResolver` configuration from untrusted templates - Implemented additional safeguards around ELResolver configuration 4. **Collection Type Validation** - Implemented proper type validation in `HubLELResolver` to prevent collection type wrapping bypasses - Added checks for wrapped types in collection deserialization - Implemented validation for all types within collections against allowlists 5. **ObjectMapper Restrictions** - Added additional restrictions on `ObjectMapper.enableDefaultTyping()` to prevent enabling via less restrictive ELResolver - Ensured default typing cannot be enabled without proper authorization **Information for Users**: Upgrade to version 2.8.3 or 2.7.6 or later to address this vulnerability. ## References ### Project Resources - **Jinjava Source Code**: [github.com/HubSpot/jinjava](https://github.com/HubSpot/jinjava) - **Jinjava Releases**: [github.com/HubSpot/jinjava/releases](https://github.com/HubSpot/jinjava/releases) ### Security Standards & Classifications - **CWE-502**: Deserialization of Untrusted Data - **CWE-913**: Improper Control of Dynamically-Managed Code Resources - **CWE-94**: Improper Control of Generation of Code ('Code Injection') - **CVSS v3.1**: Common Vulnerability Scoring System ### Additional Resources - [OWASP Template Injection](https://owasp.org/www-community/attacks/Server_Side_Template_Injection) - [Java Deserialization Security](https://cheatsheetseries.owasp.org/cheatsheets/Deserialization_Cheat_Sheet.html) - [CVE Standards and Procedures](https://cve.mitre.org/)

JinJava es un motor de plantillas basado en Java, basado en la sintaxis de plantillas de Django, adaptado para renderizar plantillas Jinja. Antes de las versiones 2.7.6 y 2.8.3, JinJava es vulnerable a la ejecución arbitraria de Java a través de un bypass mediante ForTag. Esto permite la instanciación arbitraria de clases Java y el acceso a archivos eludiendo las restricciones de sandbox integradas. Este problema ha sido parcheado en las versiones 2.7.6 y 2.8.3.