GHSA-GRR9-747V-XVCP

When Scriban renders an object that contains a circular reference, it traverses the object's members infinitely. Because the ObjectRecursionLimit property defaults to unlimited, this behavior exhausts the thread's stack space, triggering an uncatchable StackOverflowException that immediately terminates the hosting process.

When rendering objects (e.g., {{ obj }}), the Scriban rendering engine recursively inspects and formats the object's properties. To prevent infinite loops caused by deeply nested or circular data structures, TemplateContext contains an ObjectRecursionLimit property.

However, this property currently defaults to 0 (unlimited). If the data context pushed into the template contains a circular reference, the renderer will recurse indefinitely. This is especially dangerous for web applications that map user-controlled payloads (like JSON) directly to rendering contexts, or for applications that pass ORM objects (like Entity Framework models, which frequently contain circular navigation properties) into the template.

Proof of Concept (PoC)

The following C# code demonstrates the vulnerability. Executing this will cause an immediate, fatal StackOverflowException, bypassing any standard error handling.

using Scriban;
using Scriban.Runtime;

var template = Template.Parse("{{ a }}");
var context = new TemplateContext();
var a = new ScriptObject();

// Introduce a cycle
a["self"] = a;
context.PushGlobal(new ScriptObject { { "a", a } });

try {
  // This crashes the entire process immediately
  template.Render(context);
} catch (Exception ex) {
  // This will never execute because StackOverflowException
  Console.WriteLine("Caught exception: " + ex.Message);
}

Suggested Remediation

Update TemplateContext.cs to set ObjectRecursionLimit to a safe default, such as 20.

public int ObjectRecursionLimit { get; set; } = 20;

By implementing this default, circular references will gracefully result in a catchable ScriptRuntimeException rather than a fatal process crash.

This vulnerability allows a Denial of Service (DoS) attack. If a malicious user can manipulate the data structure passed to the renderer to include a cyclic reference, or if the application passes a complex object graph to an untrusted template, the entire .NET hosting process will crash.

GHSA-GRR9-747V-XVCP has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (6.6.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is GHSA-GRR9-747V-XVCP? GHSA-GRR9-747V-XVCP is a high-severity security vulnerability in scriban (nuget), affecting versions <= 6.5.8. It is fixed in 6.6.0.
2. How severe is GHSA-GRR9-747V-XVCP? GHSA-GRR9-747V-XVCP has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of scriban are affected by GHSA-GRR9-747V-XVCP? scriban (nuget) versions <= 6.5.8 is affected.
4. Is there a fix for GHSA-GRR9-747V-XVCP? Yes. GHSA-GRR9-747V-XVCP is fixed in 6.6.0. Upgrade to this version or later.
5. Is GHSA-GRR9-747V-XVCP exploitable, and should I be worried? Whether GHSA-GRR9-747V-XVCP is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether GHSA-GRR9-747V-XVCP is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix GHSA-GRR9-747V-XVCP? Upgrade scriban to 6.6.0 or later.

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