GHSA-xcx6-vp38-8hr5: Scriban has Uncontrolled Recursion in `object.to_json` Causing Unrecoverable Process Crash via StackOverflowException
Summary
The object.to_json builtin function in Scriban performs recursive JSON serialization via an internal WriteValue() static local function that has no depth limit, no circular reference detection, and no stack overflow guard. A Scriban template containing a self-referencing object passed to object.to_json triggers unbounded recursion, causing a StackOverflowException that terminates the hosting .NET process. This is a fatal, unrecoverable crash — StackOverflowException cannot be caught by user code in .NET.
Details
The vulnerable code is the WriteValue() static local function at src/Scriban/Functions/ObjectFunctions.cs:494:
static void WriteValue(TemplateContext context, Utf8JsonWriter writer, object value)
{
var type = value?.GetType() ?? typeof(object);
if (value is null || value is string || value is bool ||
type.IsPrimitiveOrDecimal() || value is IFormattable)
{
JsonSerializer.Serialize(writer, value, type);
}
else if (value is IList || type.IsArray) {
writer.WriteStartArray();
foreach (var x in context.ToList(context.CurrentSpan, value))
{
WriteValue(context, writer, x); // recursive, no depth check
}
writer.WriteEndArray();
}
else {
writer.WriteStartObject();
var accessor = context.GetMemberAccessor(value);
foreach (var member in accessor.GetMembers(context, context.CurrentSpan, value))
{
if (accessor.TryGetValue(context, context.CurrentSpan, value, member, out var memberValue))
{
writer.WritePropertyName(member);
WriteValue(context, writer, memberValue); // recursive, no depth check
}
}
writer.WriteEndObject();
}
}
This function has none of the safety mechanisms present in other recursive paths:
- ObjectToString() at TemplateContext.Helpers.cs:98 checks ObjectRecursionLimit (default 20)
- `E
Details
Original advisory: https://github.com/advisories/GHSA-xcx6-vp38-8hr5
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