External risk intelligence

Winter CMS Twig Sandbox Escape Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.3)

CVE-2026-79774

This vulnerability requires an authenticated backend user with specific template-editing permissions. While the application itself may be web-accessible, the exploitation of this feature is gated behind administrative authentication and high-privilege authorization, making it unlikely to be reachable by a typical internet-based attack surface.

Remote Code Execution

Halo Surface Signal: 2 out of 5 — less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

Winter CMS versions prior to 1.2.13 contain a vulnerability allowing authenticated users with template-editing privileges to execute arbitrary code by injecting PHP into template code sections. This could lead to unauthorized access, modification, or deletion of database records and remote code execution.

Allows code injection via template editing.
High-impact risk for authenticated users.
Confirm relevance and internal exposure.

Attack Path

How an attacker could exploit the issue

An attacker with authenticated access and template-editing permissions in the Winter CMS backend can exploit a flaw in the Twig sandbox to bypass security restrictions. By leveraging method forwarding through Eloquent models and query builders, they can execute arbitrary SQL, modify database records, and potentially achieve remote code execution by injecting PHP code into templates.

Authenticated backend user with template editing.
Bypasses Twig sandbox restrictions via method forwarding.
Leads to database manipulation and code execution.

Live Threat

Current exploitation, exposure, and threat context

Authenticated backend users with template-editing permissions could exploit this vulnerability to read and modify arbitrary database records, execute arbitrary SQL, and potentially achieve remote code execution. This is possible by bypassing sandbox restrictions through method forwarding to Eloquent models and query builders.

Database records and SQL execution.
Authenticated user bypasses sandbox.
Unauthorized data access and code execution.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability requires authenticated users with template-editing permissions within Winter CMS. Application owners or platform teams managing the CMS instances are the most likely to be responsible for addressing this. The initial step should involve identifying all instances of Winter CMS, assessing their exposure, and confirming the business criticality of any affected systems before planning remediation.

Application owners should own the issue.
Verify affected Winter CMS instances and reachability.
Plan remediation based on risk and criticality.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

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Frequently asked questions

What is Winter CMS?

Winter CMS is a free, open-source content management system built on top of the Laravel PHP framework. It is widely used for creating and managing web applications and websites, providing a structured environment where developers use the Twig templating engine to define how content is rendered. The system includes a backend administrative interface that allows authorized users to manage site templates and database configurations.

What does the Twig sandbox escape in CVE-2026-79774 mean?

This vulnerability relates to a protection mechanism called the Twig sandbox, which is designed to limit what code can be executed within templates. The weakness, categorized as CWE-693 (Protection Mechanism Failure), occurs because the sandbox's security policy is incomplete. This allows an attacker to bypass intended restrictions and access unauthorized functionality, effectively turning a restricted template editing process into an avenue for executing unauthorized commands.

How does an attacker trigger this vulnerability?

The vulnerability requires the attacker to already have valid backend credentials and specific permissions to edit templates. It does not trigger from an unauthenticated state. The exploit works by using method forwarding to bypass the sandbox, calling powerful database and model functions that should be off-limits. If a user lacks backend access or does not have template-editing privileges, this specific path is not available to them.

Is my system at risk according to Halo Surface Signal?

Halo Surface Signal indicates that exploitation is unlikely for a typical internet-based attack surface. While your Winter CMS instance might be reachable from the internet, the vulnerability is gated behind backend administrative authentication and specific high-privilege authorization. This means an attacker cannot simply use a public web request to trigger the flaw; they must first compromise a highly privileged administrative account.

What steps should I take if I run Winter CMS?

First, inventory your systems to identify all instances running Winter CMS versions older than 1.2.13. Since the risk is primarily internal, focus on reviewing and auditing your administrative user accounts and template-editing permissions to ensure access is limited to trusted personnel. Finally, plan to update to version 1.2.13 or later, which provides the necessary fixes to properly secure the Twig sandbox and prevent method forwarding abuse.

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.