vulnerability / NVI-00017538 / Revision 1
Scriban: Uncontrolled Memory Allocation via string.pad_left/pad_right Allows Remote Denial of Service
GitHub lists this reviewed advisory for Scriban, Scriban.Signed. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
7.5 high
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
Scriban
source listed< 7.0.0
## Summary The built-in `string.pad_left` and `string.pad_right` template functions in Scriban perform no validation on the `width` parameter, allowing a template expression to allocate arbitrarily large strings in a single call. When Scriban is exposed to untrusted template input — as in the official Scriban.AppService playground deployed on Azure — an unauthenticated attacker can trigger ~1GB memory allocations with a 39-byte payload, crashing the service via `OutOfMemoryException`. ## Details `StringFunctions.PadLeft` and `StringFunctions.PadRight` (`src/Scriban/Functions/StringFunctions.cs:1181-1203`) directly delegate to .NET's `String.PadLeft(int)` / `String.PadRight(int)` with no bounds checking: ```csharp // src/Scriban/Functions/StringFunctions.cs:1181-1183 public static string PadLeft(string text, int width) { return (text ?? string.Empty).PadLeft(width); } // src/Scriban/Functions/StringFunctions.cs:1200-1202 public static string PadRight(string text, int width) { return (text ?? string.Empty).PadRight(width); } ``` The `TemplateContext.LimitToString` property (default 1MB, set at `TemplateContext.cs:147`) does **not** prevent the allocation. This limit is
Scriban.Signed
source listed< 7.0.0
## Summary The built-in `string.pad_left` and `string.pad_right` template functions in Scriban perform no validation on the `width` parameter, allowing a template expression to allocate arbitrarily large strings in a single call. When Scriban is exposed to untrusted template input — as in the official Scriban.AppService playground deployed on Azure — an unauthenticated attacker can trigger ~1GB memory allocations with a 39-byte payload, crashing the service via `OutOfMemoryException`. ## Details `StringFunctions.PadLeft` and `StringFunctions.PadRight` (`src/Scriban/Functions/StringFunctions.cs:1181-1203`) directly delegate to .NET's `String.PadLeft(int)` / `String.PadRight(int)` with no bounds checking: ```csharp // src/Scriban/Functions/StringFunctions.cs:1181-1183 public static string PadLeft(string text, int width) { return (text ?? string.Empty).PadLeft(width); } // src/Scriban/Functions/StringFunctions.cs:1200-1202 public static string PadRight(string text, int width) { return (text ?? string.Empty).PadRight(width); } ``` The `TemplateContext.LimitToString` property (default 1MB, set at `TemplateContext.cs:147`) does **not** prevent the allocation. This limit is
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-v66j-x4hw-fv9g ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.