JinJava sandbox bypass via ForTag leading to arbitrary Java execution
In JinJava (HubSpot) versions prior to 2.7.6 and 2.8.3, a sandbox bypass in template rendering allows arbitrary Java execution. The bypass is reachable via the ForTag implementation used for iterating over lists/items in templates: ForTag iterates over object properties using Java bean introspection (Introspector.getBeanInfo()) without enforcing JinJava’s Bean ELResolver restrictions, enabling invocation of getter methods that should be blocked by the sandbox. In reported exploitation chains, this can be combined with an ObjectMapper JSON deserialization path to bypass the sandbox type allowlist and instantiate otherwise-restricted classes (e.g., JinjavaConfig or JinjavaELContext), effectively weakening or rewriting sandbox rules. The net result is arbitrary Java class instantiation and file access despite built-in sandbox restrictions.
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A critical sandbox-escape leading to arbitrary Java code execution in the Jinjava Java template engine (used by HubSpot CMS), caused by a chain of bypasses involving ForTag property iteration restrictions and ObjectMapper JSON deserialization type allowlist bypass.
Arbitrary Java code execution in the JinJava template engine due to a sandbox bypass via ForTag, enabling arbitrary Java class instantiation and file access.
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