GHSA-x6m9-38vm-2xhf: Scriban Scriban Has An Authorization Bypass Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-x6m9-38vm-2xhf",
  "modified" : "2026-07-06T13:07:43Z",
  "published" : "2026-03-24T22:09:49Z",
  "aliases" : [ ],
  "summary" : "Scriban has an authorization bypass due to stale include cache surviving TemplateContext.Reset() ",
  "details" : "## Summary\n\n`TemplateContext.Reset()` claims that a `TemplateContext` can be reused safely on the same thread, but it does not clear `CachedTemplates`. If an application pools `TemplateContext` objects and uses an `ITemplateLoader` that resolves content per request, tenant, or user, a previously authorized include can be served to later renders without calling `TemplateLoader.Load()` again.\n\n## Details\n\nThe relevant code path is:\n\n- `TemplateContext.Reset()` only clears output, globals, cultures, and source files in `src/Scriban/TemplateContext.cs` lines 877–902.\n- `CachedTemplates` is initialized once and kept on the context in `src/Scriban/TemplateContext.cs` line 197.\n- `include` resolves templates through `IncludeFunction.Invoke()` in `src/Scriban/Functions/IncludeFunction.cs` lines 29–43.\n- `IncludeFunction.Invoke()` calls `TemplateContext.GetOrCreateTemplate()` in `src/Scriban/TemplateContext.cs` lines 1249–1256.\n- If a template path is already present in `CachedTemplates`, Scriban returns the cached compiled template and does **not** call `TemplateLoader.Load()` again.\n\nThis becomes a security issue when `ITemplateLoader.Load()` returns request-dependent content. A first render can prime the cache with an admin-only or tenant-specific template, and later renders on the same reused `TemplateContext` will receive that stale template even after `Reset()`.\n\n---\n\n## Proof of Concept\n\n### Setup\n\n```bash\nmkdir scriban-poc1\ncd scriban-poc1\ndotnet new console --framework net8.0\ndotnet add package Scriban --version 6.6.0\n```\n\n### `Program.cs`\n\n```csharp\nusing Scriban;\nusing Scriban.Parsing;\nusing Scriban.Runtime;\n\nvar loader = new SwitchingLoader();\nvar context = new TemplateContext\n{\n    TemplateLoader = loader,\n};\n\nvar template = Template.Parse(\"{{ include 'profile' }}\");\n\nloader.Content = \"admin-only\";\nConsole.WriteLine(\"first=\" + template.Render(context));\n\ncontext.Reset();\n\nloader.Content = \"guest-view\";\nConsole.WriteLine(\"second=\" + template.Render(context));\n\nsealed class SwitchingLoader : ITemplateLoader\n{\n    public string Content { get; set; } = string.Empty;\n\n    public string GetPath(TemplateContext context, SourceSpan callerSpan, string templateName) => templateName;\n\n    public string Load(TemplateContext context, SourceSpan callerSpan, string templatePath) => Content;\n\n    public ValueTask<string> LoadAsync(TemplateContext context, SourceSpan callerSpan, string templatePath)\n        => new(Content);\n}\n```\n\n### Run\n\n```bash\ndotnet run\n```\n\n### Actual Output\n\n```\nfirst=admin-only\nsecond=admin-only\n```\n\n### Expected Output\n\n```\nfirst=admin-only\nsecond=guest-view\n```\n\nThe second render should reload the template after `Reset()`, but it instead reuses the cached compiled template from the previous render.\n\n---\n\n## Impact\n\nThis is a cross-render data isolation issue. Any application that reuses `TemplateContext` objects and uses a request-dependent `ITemplateLoader` can leak previously authorized template content across requests, users, or tenants.\n\nThe issue impacts applications that:\n\n- Pool or reuse `TemplateContext`\n- Call `Reset()` between requests\n- Use `include`\n- Resolve include content based on request-specific state",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "scriban"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "7.0.0"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Scriban.Signed"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "7.0.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/scriban/scriban/security/advisories/GHSA-x6m9-38vm-2xhf"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/scriban/scriban"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-226" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-24T22:09:49Z",
    "nvd_published_at" : null
  }
}