Overview LangChainGo, the Go implementation of LangChain, a large language model (LLM) application building framework, has been discovered to contain an arbitrary file read vulnerability. The vulnerability, tracked as CVE-2025-9556, allows for arbitrary file read through the Gonja template engine with Jinja2 syntax. Attackers can exploit this by injecting malicious prompt content to access sensitive files, leading to a server-side template injection (SSTI) attack. Description LangChainGo is the Go Programming Language port/fork of LangChain, an open-source orchestration framework for the development of applications that leverage LLMs. LangChainGo uses Gonja for syntax parsing and creating dynamic and reusable prompt templates. Gonja is the Go implementation of Jinja2, a templating engine. Gonja is largely compatable with the the original Python Jinja2 implementation, and supports Jinja2 syntax. As Gonja supports Jinja2 syntax, an attacker could leverage directives such as {% include %}, {% from %}, or {% extends %} for malicious purposes within LangChainGo. While these directives were meant to be used for building reusable templates, they can also allow an external file to be pulled and read from the server’s filesystem. An attacker could use this to inject malicious template code containing advanced templating directives to read sensitive files such as /etc/password. This results in a server-side template injection vulnerability that can expose sensitive information. This…Read More
Langchaingo supports jinja2 and gonja for syntax parsing, allowing for arbitrary file read
