External risk intelligence

Scriban Information Disclosure and Object Manipulation Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.1)

CVE-2026-124438

Scriban is a template engine library embedded within various .NET applications. While it can be used in internet-facing web applications to render dynamic content, it is a backend component rather than a standalone service or edge gateway. Exposure depends entirely on whether an application allows untrusted users to provide or influence the templates being processed, which is a common but not universal deployment pattern.

Information Disclosure

Halo Surface Signal: 3 out of 5 — possibly public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This advisory concerns a vulnerability in the Scriban template engine that could allow unauthorized access to internal .NET information and manipulation of service properties. While the vulnerability has a critical severity score, its actual impact depends heavily on how Scriban is implemented within your applications and whether external users can influence template content. The main concern at this stage is confirming relevance and exposure within your specific environments.

Allows access to internal system details.
Matters if Scriban is used with external input.
Confirm if Scriban is used and how.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by creating specially crafted templates that leverage array.map to access internal .NET function details. This could expose sensitive information or allow for the modification of service properties and secrets.

Template authors are the entry point.
Malicious templates trigger reflection member access.
Information disclosure and object manipulation.

Live Threat

Current exploitation, exposure, and threat context

Template authors could access sensitive .NET internal information, potentially leading to the exposure and overwriting of service properties, captured secrets, and assembly paths under specific conditions.

Service properties and secrets.
Reflection access to delegate internals.
Compromise of service configuration data.

Operational Fix

Recommended remediation, mitigation, and detection steps

The real-world impact of this vulnerability hinges on how the Scriban template engine is integrated into .NET applications. Application owners and platform teams are most likely to be responsible for addressing this, as it affects how their code processes templates. The first practical step is to identify all .NET applications that use Scriban, determine if they process untrusted template input, and then assess the business criticality of those applications before planning remediation.

Identify affected .NET applications.
Verify template input is trusted.
Plan remediation based on risk.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is the Scriban library?

Scriban is a template engine library for .NET applications. Developers use it to render dynamic text or HTML, often by allowing users to define custom templates that the application then processes.

What kind of security weakness is CVE-2026-124438?

This vulnerability is classified as CWE-200, or information exposure. In Scriban, the engine incorrectly permits template code to use reflection to inspect internal .NET function details. This means an attacker can 'see' parts of the application's memory or logic that should remain hidden.

How does an attacker trigger this vulnerability?

An attacker triggers this by submitting a specially crafted template that uses the array.map function. Simply using Scriban is not enough; the engine must process malicious template content created by a user. If your application only uses hardcoded, internal templates that users cannot change, this trigger path is not active.

Do I need to worry if my Scriban application is internal?

According to Halo Surface Signal, relevance depends on whether your application allows untrusted users to influence the templates being processed. While the CVSS score reflects a network-based vector, the actual risk is tied to the input source; an internal application is still at risk if it renders user-supplied template data.

How should I respond to this threat?

Start by identifying all .NET services in your environment that rely on the Scriban library. Once mapped, verify if these services process templates from untrusted or external sources. Prioritize remediating any application that allows users to supply their own template content, as this is the primary path for exploitation.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.