Listen to this Post
Technical Deep Dive: How CVE-2026-54718 Works
The `symbiote/silverstripe-advancedworkflow` module extends the Silverstripe CMS by providing a graphical interface for creating custom approval workflows, embargo/expiry rules, and automated email notifications. A core feature of this module allows CMS users with workflow administration permissions to configure notification email templates through a plain text area field. This field’s content is rendered server‑side as a Silverstripe template, meaning the system processes any Silverstripe‑specific markup embedded in the email body before sending it.
The root cause of CVE‑2026‑54718 lies in the Silverstripe template engine’s handling of the `<%t %>` translation block. Prior to the patch, the template compiler would emit the default string and the context string of a `<%t %>` block directly as double‑quoted PHP string literals inside the compiled PHP template. In PHP, double‑quoted strings interpolate variables and expressions—including variable‑variable constructs (e.g., ${$var}) and complex function calls. This behaviour is not inherently dangerous when the template content is trusted, but it becomes critical when an attacker can control the template source.
In the Advanced Workflow module, any user who has permission to create or edit workflows can modify the email template field. An attacker with such privileges can inject a malicious `<%t %>` block into the email template. Inside that block, they can craft a default string that contains a PHP variable‑variable expression—for example, `${${eval($_POST[‘cmd’])}}` or a similar payload that executes arbitrary PHP code. When the workflow engine renders the email template to send a notification, the template compiler processes the `<%t %>` block and writes the attacker’s payload as a double‑quoted PHP string into the cached compiled template file. Subsequently, when that compiled template is included and executed by the PHP runtime, the variable‑variable expression is evaluated, leading to remote code execution on the server.
This vulnerability is particularly dangerous because it does not require any direct file upload or complex request forgery—only the ability to modify a workflow’s email template through the CMS administrative interface. The attack vector is network‑accessible, requires low attack complexity, demands high privileges (CMS user with workflow permissions), and results in full compromise of confidentiality, integrity, and availability (CVSS 7.2). The issue was reported by Steve Boyd of Silverstripe Ltd. and patched by modifying the template parser to emit default and context strings as single‑quoted PHP string literals, which do not interpolate variables or expressions, thereby neutralising the injection vector. The fix was applied upstream in `silverstripe/framework` for CMS 5.4 and in `silverstripe/template-engine` for CMS 6.1 and 6.2, and the Advanced Workflow module was updated to require a fixed version of these dependencies.
DailyCVE Form:
Platform: Silverstripe CMS
Version: <6.4.5, 7.0.0-7.1.2, 7.2.0
Vulnerability: Remote Code Execution
Severity: High (CVSS 7.2)
date: 2026-06-24
Prediction: 2026-07-01 (estimated patch availability)
What Undercode Say:
Check installed version of symbiote/silverstripe-advancedworkflow composer show symbiote/silverstripe-advancedworkflow List all versions available (including patched ones) composer show symbiote/silverstripe-advancedworkflow --all Upgrade to the latest patched version (e.g., 7.2.1) composer require symbiote/silverstripe-advancedworkflow:^7.2.1 For CMS 5.4 environments, ensure framework is updated to fixed version composer require silverstripe/framework:^5.4.0 Verify that the template engine fix is applied (CMS 6.1+) composer require silverstripe/template-engine:^6.1.0
Code Snippet – Vulnerable Template Compilation (Pre‑Patch):
// Simplified representation of the vulnerable compiler output // The default string from <%t 'Hello $name' %> is emitted as: $translated = "Hello $name"; // Double-quoted → interpolates $name
Code Snippet – Patched Compilation (Post‑Patch):
// After the fix, the same block is emitted as: $translated = 'Hello $name'; // Single-quoted → no interpolation
Exploit: (Educational Purposes!)
An authenticated CMS user with workflow management permissions can perform the following steps to achieve RCE:
1. Navigate to the Workflow Admin section in the CMS.
2. Create a new workflow or edit an existing one.
3. Locate the email template field (used for notification emails).
4. Inject a payload into the template using the `<%t %>` translation block, for example:
<%t '${${eval($_POST["x"])}}' %>
or more concretely:
<%t '${${system("id")}}' %>
5. Save the workflow.
- Trigger the workflow (e.g., by publishing a page that uses the workflow, or by manually executing the workflow action).
- When the email is rendered, the compiled template executes the injected PHP code, granting the attacker arbitrary command execution on the server.
Note: This exploit requires the attacker to have high‑privilege CMS access. It is not exploitable by unauthenticated or low‑privileged users.
Protection
- Upgrade the `symbiote/silverstripe-advancedworkflow` module to one of the following patched versions: 6.4.5, 7.1.3, or 7.2.1.
- Ensure that the underlying Silverstripe CMS dependencies are also updated:
- For CMS 5.4: upgrade `silverstripe/framework` to a version that includes the template‑parser fix.
- For CMS 6.1 and 6.2: upgrade `silverstripe/template-engine` to the fixed version.
- If an immediate upgrade is not possible, restrict workflow creation and editing permissions to only the most trusted administrators.
- Audit existing workflow email templates for any suspicious `<%t %>` blocks or unusual PHP‑like syntax.
- Monitor server logs for unexpected PHP errors or outbound connections originating from the web server process.
- Subscribe to the Silverstripe security release RSS feed and pre‑announcement mailing list to receive timely notifications of future vulnerabilities.
Impact
Successful exploitation of CVE‑2026‑54718 allows an attacker to execute arbitrary PHP code on the server with the privileges of the web server user. This can lead to:
– Full system compromise: The attacker can read, modify, or delete any file accessible to the web server, including sensitive configuration files, database credentials, and application source code.
– Data breach: All data stored in the CMS (including user records, content, and private documents) can be exfiltrated.
– Lateral movement: The compromised server can be used as a pivot point to attack internal networks or other services.
– Denial of service: The attacker can disrupt the website or the entire server by deleting critical files or overloading system resources.
– Persistence: Backdoors can be planted to maintain long‑term access even after the vulnerability is patched.
Given the CVSS score of 7.2 (High) and the relative ease of exploitation for authenticated high‑privilege users, this vulnerability poses a significant risk to any Silverstripe installation that uses the Advanced Workflow module with untrusted or semi‑trusted CMS administrators. All site owners are strongly advised to apply the available patches without delay.
🎯Let’s Practice Exploiting & Learn Patching For Free:
🎓 Live Courses & Certifications:
Join Undercode Academy for Verified Certifications
🚀 Request a Custom Project:
Secure, high-velocity infrastructure and disruptive technological engineering. Contact our engineering team for high-tier development and proprietary systems:
[email protected]
💎 Smart Architecture | 🛡️ Secure by Design | ⭐ Trusted by Thousands
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
