GHSA-WGH7-7M3C-FX25

Scriban is vulnerable to an uncontrolled process crash resulting in a Denial of Service. Because the recursive-descent parser does not enforce a default limit on expression depth, an attacker who controls template input can craft a heavily nested template that triggers a StackOverflowException. In .NET, a StackOverflowException cannot be caught by standard try-catch blocks, resulting in the immediate and ungraceful termination of the entire hosting process.

Scriban utilizes a recursive-descent parser to process template expressions. While the library exposes an ExpressionDepthLimit property in its ParserOptions, this property defaults to null (disabled).

If an application accepts user-supplied templates (or dynamically constructs templates from untrusted input), an attacker can supply thousands of nested parentheses or blocks. As the parser recursively evaluates each nested layer, it consumes thread stack space until it exceeds the limits of the host OS, triggering a fatal crash.

Proof of Concept (PoC)

The following C# code demonstrates the vulnerability. Executing this code will immediately terminate the application process.

using Scriban;

// Creates a deeply nested expression: (((( ... (1) ... ))))
string nested = new string('(', 10000) + "1" + new string(')', 10000);

try {
  // This will crash the entire process immediately
  Scriban.Template.Parse("{{ " + nested + " }}");
} catch (Exception ex) {
  // This catch block will never execute because StackOverflowException
  Console.WriteLine("Caught exception: " + ex.Message);
}

Suggested Remediation

Update the ParserOptions constructor (or the internal parser initialization) to set a default value for ExpressionDepthLimit. A limit of 1000 (or even lower, such as 250 or 500) is generally more than enough for legitimate templates while safely preventing stack exhaustion.

public int? ExpressionDepthLimit { get; set; } = 250; 

Alternatively, document the risk heavily and warn developers to manually set ExpressionDepthLimit if evaluating untrusted templates, though a secure-by-default approach is strongly preferred.

An attacker can supply crafted input that triggers a StackOverflowException, causing immediate termination of the hosting process and resulting in a Denial of Service. In applications that process untrusted or user-controlled templates (e.g., web applications or APIs), this can be exploited remotely without authentication. The failure is not recoverable, requiring a full process restart and leading to service disruption.

GHSA-WGH7-7M3C-FX25 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-WGH7-7M3C-FX25? GHSA-WGH7-7M3C-FX25 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-WGH7-7M3C-FX25? GHSA-WGH7-7M3C-FX25 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-WGH7-7M3C-FX25? scriban (nuget) versions <= 6.5.8 is affected.
4. Is there a fix for GHSA-WGH7-7M3C-FX25? Yes. GHSA-WGH7-7M3C-FX25 is fixed in 6.6.0. Upgrade to this version or later.
5. Is GHSA-WGH7-7M3C-FX25 exploitable, and should I be worried? Whether GHSA-WGH7-7M3C-FX25 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-WGH7-7M3C-FX25 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-WGH7-7M3C-FX25? Upgrade scriban to 6.6.0 or later.