CVE-2026-74789: Scriban LoopLimit denial-of-service bypass in built-in operations

CVE-2026-74789 · Severity: high · CVSS 7.5 · Published 2026-08-16

Scriban is a templating engine used in applications to safely render user-controlled templates. A flaw allows attackers to bypass the LoopLimit safety mechanism—a resource constraint designed to prevent templates from consuming excessive CPU or memory—by crafting single expressions that iterate internally without triggering the safety check. An attacker can submit malicious template code that forces millions of iterations or gigabytes of memory allocation, causing denial of service even when LoopLimit is set to permit only one iteration.

Technologies: scriban (NuGet), Scriban.Signed (NuGet). Vendors: NuGet.

Quick answers

Is CVE-2026-74789 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-74789 being exploited in the wild.
How severe is CVE-2026-74789?
High severity, with a CVSS score of 7.5, published 16 August 2026.
Which products and versions are affected?
scriban (NuGet) ECOSYSTEM:introduced=0,fixed=7.0.0; Scriban.Signed (NuGet) ECOSYSTEM:introduced=0,fixed=7.0.0.
Is there a fix for CVE-2026-74789?
Yes. scriban (NuGet): upgrade to 7.0.0 or later; Scriban.Signed (NuGet): upgrade to 7.0.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-74789 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-74789?
Check whether you run scriban (NuGet) or Scriban.Signed (NuGet) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • scriban (NuGet): upgrade to 7.0.0 or later
    dotnet add package scriban --version 7.0.0
  • Scriban.Signed (NuGet): upgrade to 7.0.0 or later
    dotnet add package Scriban.Signed --version 7.0.0

Technical details

Scriban's LoopLimit constraint is enforced only during script loop statement execution via TemplateContext.StepLoop(), but built-in operations like array iteration and string multiplication perform expensive internal work without invoking this check. A ScriptRange created from expressions like 1..1000000 yields elements sequentially without calling StepLoop(), and string multiplication in ScriptBinaryExpression.CalculateToString() uses a plain for loop unguarded by LoopLimit. Attackers with the ability to submit template content can exploit this with expressions such as {{ 1..1000000 | array.size }} or {{ 'A' * 200000000 }} to trigger uncontrolled resource consumption regardless of the configured LoopLimit value. The vulnerability affects any application rendering untrusted templates that relies on LoopLimit for containment. A patch is available in version 7.0.0.

Affected products

  • Scriban Scriban <= 6.6.0

Identifiers

  • CVE-2026-74789
  • GHSA-c875-h985-hvrc

Timeline

  • 2026-03-22: disclosed
  • 2026-08-16: advisory
  • 2026: patched: Version 7.0.0

References

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