Horizon Alert
Summary of the vulnerability and why it matters
This advisory details a critical vulnerability in Grav's Flex form functionality, enabling unauthorized users with editing permissions to execute arbitrary code by manipulating form field names. This could lead to the deletion or overwriting of files and directories on affected systems.
- Allows unauthorized code execution through form manipulation.
- Critical vulnerability impacting file integrity and system access.
- Confirm relevance and exposure of affected Grav instances.
Attack Path
How an attacker could exploit the issue
An attacker could start with an account that has page-editing permissions on a Grav website. By manipulating Flex form fields, the attacker can bypass security checks and execute arbitrary public static methods. This allows them to perform actions like deleting directories, overwriting files, or reading sensitive files on the server.
- Requires page editor permissions.
- Trick form processor to call methods.
- Delete files, overwrite, or read data.
Live Threat
Current exploitation, exposure, and threat context
A vulnerability in Grav could allow authenticated users with page-edit permissions to invoke arbitrary public static methods. This could lead to the deletion or modification of files and directories on the server.
- Server files and directories could be affected.
- Maliciously crafted form field names could be used.
- Unauthorized file deletion or reading may occur.
Operational Fix
Recommended remediation, mitigation, and detection steps
This vulnerability impacts Grav installations with administrative or page-editing access. The first step is to identify all Grav instances, determine their exposure and criticality, and pinpoint the accountable application or platform owner. Remediation planning should then proceed based on assessed risk.
- Application owners should manage the issue.
- Verify administrative access and exposure.
- Plan and schedule updates or vendor coordination.
