Skip to main content

LangChainGo vulnerability CVE-2025-9556 identified

Source Decision Insights Threat Desk Published September 16, 2025
Human View Machine View

Best suited for

Persona
Security Operations Leader
Decision stage
Which to buy
Adoption curve
Early Adopters

Our classification, not the publisher's statement. Best suited for, not only for.

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 vulnerability is tracked as CVE-2025-9556.

Impact

This vulnerability compromises the confidentiality of the system by enabling arbitrary file read on a server running LangChainGo. By injecting malicious template syntax, an attacker could access sensitive information stored on the victim device. This information can lead to further comprise of the system. In LLM-based chatbot environments that use LangChainGo, attackers would only need access to the prompt to maliciously craft and exploit the prompt.

Solution

The maintainer of LangChainGo has released with new security features to prevent template injection. A new RenderTemplateFS function has been added, which supports secure file template referencing, on top of blocking filesystem access by default. Users of LangChainGo should update to the latest version of the software in order to be protected.

Acknowledgements

Thanks to the reporter, bestlzk. This document was written by Ayushi Kriplani and Christopher Cullen.

Vendor Information

One or more vendors are listed for this advisory. Please reference the full report for more information.

References

Other Information

Common Vulnerabilities and Exposures (CVE) Intrusion Detection System (IDS): CVE-2025-9556
Date Public: 2025-09-12
Date First Published: 2025-09-12
Date Last Updated: 2025-09-12 13:44 UTC
Document Revision: 1

Blog post, originally published by Ayushi Kriplani and Christopher Cullen at kb.cert.org.

Mentions

Structured data (JSON-LD)

The schema.org markup this page publishes for search engines and AI agents, exactly as they read it.

[
  {
    "@context": "https://schema.org",
    "@id": "https://decisioninsights.ai/#website",
    "@type": "WebSite",
    "name": "Decision Insights",
    "potentialAction": {
      "@type": "SearchAction",
      "target": {
        "@type": "EntryPoint",
        "urlTemplate": "https://decisioninsights.ai/search/?q={search_term_string}&submit=1"
      }
    },
    "publisher": {
      "@id": "https://decisioninsights.ai/#organization"
    },
    "url": "https://decisioninsights.ai"
  },
  {
    "@context": "https://schema.org",
    "@id": "https://decisioninsights.ai/#organization",
    "@type": "Organization",
    "contactPoint": {
      "@type": "ContactPoint",
      "contactType": "customer support",
      "email": "[email protected]"
    },
    "description": "Decision Insights is a Registry of technology companies, open source projects, and industry terms, built for people and for AI agents that need sourced, structured information.",
    "logo": {
      "@type": "ImageObject",
      "url": "https://wiretap-cdn-assets.nyc3.cdn.digitaloceanspaces.com/decision-insights/[email protected]"
    },
    "name": "Decision Insights",
    "parentOrganization": {
      "@type": "Organization",
      "name": "Wiretap Labs",
      "sameAs": [
        "https://www.linkedin.com/company/wiretap-labs",
        "https://www.crunchbase.com/organization/wiretap-labs"
      ],
      "url": "https://wiretaplabs.com"
    },
    "publishingPrinciples": "https://decisioninsights.ai/standards/",
    "sameAs": [
      "https://www.linkedin.com/company/decisioninsights"
    ],
    "url": "https://decisioninsights.ai"
  },
  {
    "@context": "https://schema.org",
    "@type": "BreadcrumbList",
    "itemListElement": [
      {
        "@type": "ListItem",
        "item": "https://decisioninsights.ai",
        "name": "Decision Insights",
        "position": 1
      },
      {
        "@type": "ListItem",
        "item": "https://decisioninsights.ai/records/",
        "name": "Records",
        "position": 2
      },
      {
        "@type": "ListItem",
        "item": "https://decisioninsights.ai/langchaingo-vulnerability-cve-2025-9556-identified/",
        "name": "LangChainGo vulnerability CVE-2025-9556 identified",
        "position": 3
      }
    ]
  },
  {
    "@context": "https://schema.org",
    "@id": "https://decisioninsights.ai/langchaingo-vulnerability-cve-2025-9556-identified/#blogposting",
    "@type": "BlogPosting",
    "audience": [
      {
        "@type": "Audience",
        "additionalType": "Persona",
        "audienceType": "Security Operations Leader"
      },
      {
        "@type": "Audience",
        "additionalType": "Adoption curve",
        "audienceType": "Early Adopters"
      }
    ],
    "author": {
      "@id": "https://decisioninsights.ai/author/decision-insights-threat-desk/#person",
      "@type": "Person",
      "name": "Decision Insights Threat Desk",
      "url": "https://decisioninsights.ai/author/decision-insights-threat-desk/"
    },
    "dateModified": "2026-08-23T13:33:31-06:00",
    "datePublished": "2025-09-16T10:11:56-06:00",
    "description": "LangChainGo vulnerability CVE-2025-9556 allows arbitrary file read; update to new version to mitigate risks associated with exposure.",
    "headline": "LangChainGo vulnerability CVE-2025-9556 identified",
    "isBasedOn": {
      "@type": "CreativeWork",
      "author": {
        "@type": "Person",
        "name": "Ayushi Kriplani and Christopher Cullen"
      },
      "sourceOrganization": {
        "@id": "https://decisioninsights.ai/registry/department-of-homeland-security/#organization",
        "@type": "Organization",
        "mainEntityOfPage": "https://decisioninsights.ai/registry/department-of-homeland-security/",
        "name": "Department of Homeland Security"
      },
      "url": "https://kb.cert.org/vuls/id/949137"
    },
    "keywords": [
      "Common Vulnerabilities and Exposures",
      "Exploit",
      "Intrusion Detection System",
      "Server",
      "Vulnerabilities"
    ],
    "mainEntityOfPage": {
      "@id": "https://decisioninsights.ai/langchaingo-vulnerability-cve-2025-9556-identified/",
      "@type": "WebPage",
      "sdDatePublished": "2026-08-23",
      "sdPublisher": {
        "@id": "https://decisioninsights.ai/#organization"
      }
    },
    "mentions": [
      {
        "@id": "https://decisioninsights.ai/projects/python/#project",
        "@type": "SoftwareSourceCode",
        "mainEntityOfPage": "https://decisioninsights.ai/projects/python/",
        "name": "Python"
      }
    ],
    "publisher": {
      "@id": "https://decisioninsights.ai/#organization"
    }
  },
  {
    "@context": "https://schema.org",
    "@id": "https://decisioninsights.ai/author/decision-insights-threat-desk/#person",
    "@type": "Person",
    "description": "CISA advisories, vendor security bulletins, and CVE disclosures, summarized into sourced briefs. Produced under our Standards & Methodology.",
    "name": "Decision Insights Threat Desk",
    "sameAs": [
      "https://www.linkedin.com/showcase/decisioninsights/"
    ],
    "url": "https://decisioninsights.ai/author/decision-insights-threat-desk/"
  }
]

Is this your company? Get structured data for your own pages