CVE-2026-26046 Overview
A command injection vulnerability exists in Moodle's TeX filter administrative setting due to insufficient sanitization of configuration input. This vulnerability allows authenticated administrators to inject and execute arbitrary system commands on servers where the TeX filter is enabled and ImageMagick is installed. While exploitation requires administrative privileges, successful compromise could result in complete server takeover, affecting the entire Moodle installation and its underlying infrastructure.
Critical Impact
Authenticated administrators can achieve remote code execution through maliciously crafted TeX filter configuration values, potentially compromising the entire Moodle server and all associated data.
Affected Products
- Moodle (multiple versions affected)
- Moodle installations with TeX filter enabled
- Moodle servers with ImageMagick installed
Discovery Timeline
- 2026-02-21 - CVE-2026-26046 published to NVD
- 2026-02-26 - Last updated in NVD database
Technical Details for CVE-2026-26046
Vulnerability Analysis
This vulnerability is classified as CWE-78 (Improper Neutralization of Special Elements used in an OS Command), commonly known as OS Command Injection. The flaw resides in the TeX filter administrative settings within Moodle's configuration interface. When an administrator configures TeX filter settings, the input values are insufficiently sanitized before being passed to system commands, particularly those interacting with ImageMagick for rendering mathematical expressions.
The vulnerability specifically manifests when processing TeX-related configuration parameters that are subsequently used in command-line operations. Because the input sanitization is inadequate, an attacker with administrative access can craft malicious configuration values containing shell metacharacters or command sequences that execute arbitrary system commands when the TeX filter processes content.
Root Cause
The root cause of this vulnerability is improper input validation and sanitization within the TeX filter configuration handling code. Configuration values entered by administrators are not adequately escaped or validated before being incorporated into shell commands executed by the ImageMagick image processing pipeline. This allows shell metacharacters and command injection payloads to be interpreted by the underlying operating system shell.
Attack Vector
The attack requires network access and administrative privileges to the Moodle installation. An attacker with administrator credentials can navigate to the TeX filter settings and inject malicious command sequences into configuration fields. When Moodle subsequently invokes ImageMagick to render TeX content, the injected commands are executed with the privileges of the web server process.
The attack flow involves:
- Authenticating to Moodle with administrator privileges
- Navigating to the TeX filter configuration settings
- Injecting shell commands into vulnerable configuration fields
- Triggering the TeX rendering process to execute the payload
Because this requires administrator access, the attack surface is limited. However, compromised admin credentials, insider threats, or privilege escalation from lower-privileged accounts could enable exploitation.
Detection Methods for CVE-2026-26046
Indicators of Compromise
- Unusual configuration changes in TeX filter settings containing shell metacharacters such as ;, |, $(), or backticks
- Unexpected processes spawned by the web server user when processing TeX content
- Anomalous outbound network connections from the Moodle server
- Unauthorized modifications to system files or creation of new user accounts
- Suspicious entries in web server and system logs related to ImageMagick execution
Detection Strategies
- Monitor Moodle administrative logs for changes to TeX filter configuration settings
- Implement file integrity monitoring on critical Moodle configuration files
- Deploy endpoint detection solutions to identify anomalous process execution chains originating from the web server
- Review web application firewall logs for requests containing command injection patterns targeting administrative endpoints
Monitoring Recommendations
- Enable verbose logging for Moodle administrative actions and configuration changes
- Configure alerts for any modifications to TeX filter settings by any administrator
- Implement process monitoring to detect unexpected child processes spawned by Apache/Nginx workers
- Establish baseline behavior for ImageMagick execution and alert on deviations
How to Mitigate CVE-2026-26046
Immediate Actions Required
- Review and audit all current TeX filter configuration settings for suspicious values
- Temporarily disable the TeX filter if not actively required for educational content
- Restrict administrative access to the minimum necessary personnel
- Implement additional authentication controls for administrative functions
- Review administrator account activity for signs of compromise
Patch Information
Organizations should monitor Moodle's official security advisories for patch releases addressing CVE-2026-26046. Additional information is available through the Red Hat CVE-2026-26046 Advisory and Red Hat Bug #2440903. Apply security patches as soon as they become available from Moodle or your distribution vendor.
Workarounds
- Disable the TeX filter entirely if mathematical notation rendering is not required
- Remove or disable ImageMagick on the Moodle server if not essential for operations
- Implement network segmentation to limit the impact of potential server compromise
- Apply strict input validation at the web application firewall level for administrative endpoints
- Consider implementing a dedicated, isolated environment for TeX rendering with restricted system access
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
