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Craft CMS: Authenticated leak of secret environment variables

Moderate severity GitHub Reviewed Published Jul 25, 2026 in craftcms/cms • Updated Sep 1, 2026

Package

composer craftcms/cms (Composer)

Affected versions

>= 5.0.0-RC1, < 5.10.6
>= 4.0.0-RC1, < 4.18.2

Patched versions

5.10.6
4.18.2

Description

Environment variables and secrets are interpolated into a Twig template even when the Twig sandbox is enabled, allowing them to be leaked by an authenticated attacker.

The Craft vulnerability CVE-2026-31857 was only patched by applying sandboxed Twig templating. This theoretically protects Craft CMS against RCE attacks, provided the sandbox is enabled and secure, with no known bypasses.

However, the same request parameter elementId, which allows for sandboxed Twig templates to be rendered, also includes functionality that interpolates referenced environment variables. If the parameter includes a string of the form ${ENV_VAR} then the string is replaced with the environment variable or secret from a secrets file with that name.

Afterward, the string is rendered as a Twig template. If the sandbox is disabled, Twig templates can already gain RCE or access environment variables using the getenv function. Sandboxed Twig templates should not have this access, but now do thanks to this additional environment-variable replacement behavior.

The template’s resulting value is not directly reflected in the response. To exfiltrate the value, the sandboxed Twig template cannot use network functions. But it can use a blind error-based approach similar to blind SQL injection. With enough requests, any environment variable or secret can be incrementally leaked. This can be abused to forge a session, escalate privileges with the CRAFT_SECURITY_KEY, and steal credentials for the database, SMTP server, or other connected APIs or blob storage.

Impact

An authenticated attacker, with permission to access the control panel, can render a malicious Twig template and steal arbitrary environment variables and secrets with a large number of requests, even if the Twig sandbox is enabled through enableTwigSandbox().

References

@angrybrad angrybrad published to craftcms/cms Jul 25, 2026
Published to the GitHub Advisory Database Aug 6, 2026
Reviewed Aug 6, 2026
Last updated Sep 1, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required High
User interaction None
Vulnerable System Impact Metrics
Confidentiality Low
Integrity None
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(13th percentile)

Weaknesses

Exposure of Resource to Wrong Sphere

The product exposes a resource to the wrong control sphere, providing unintended actors with inappropriate access to the resource. Learn more on MITRE.

CVE ID

CVE-2026-72782

GHSA ID

GHSA-596p-6jv8-775v

Source code

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