CVE-2026-25691: FortiSandbox Path Traversal Vulnerability

CVE-2026-25691 Overview

A path traversal vulnerability (CWE-22) has been identified in Fortinet FortiSandbox products that allows a privileged attacker with super-admin profile and CLI access to delete arbitrary directories via specially crafted HTTP requests. This vulnerability affects multiple versions of FortiSandbox including on-premises, cloud, and PaaS deployments.

Critical Impact

Privileged attackers can exploit this path traversal flaw to delete arbitrary directories on affected FortiSandbox systems, potentially causing significant data loss, service disruption, or compromising the integrity of sandboxed malware analysis operations.

Affected Products

• Fortinet FortiSandbox 5.0.0 through 5.0.5
• Fortinet FortiSandbox 4.4.0 through 4.4.8
• Fortinet FortiSandbox 4.2 all versions
• Fortinet FortiSandbox Cloud 5.0.4
• Fortinet FortiSandbox PaaS 5.0.4

Discovery Timeline

• 2026-04-14 - CVE-2026-25691 published to NVD
• 2026-04-14 - Last updated in NVD database

Technical Details for CVE-2026-25691

Vulnerability Analysis

This vulnerability is classified as an Improper Limitation of a Pathname to a Restricted Directory, commonly known as path traversal or directory traversal (CWE-22). The flaw exists in how FortiSandbox processes HTTP requests containing file system paths, allowing attackers to escape intended directory restrictions.

The vulnerability requires elevated privileges to exploit, specifically a super-admin profile with CLI access. While this requirement limits the potential attack surface, organizations must consider insider threats, compromised administrator credentials, or lateral movement scenarios where an attacker has already obtained privileged access to the FortiSandbox management interface.

The impact of successful exploitation includes the ability to delete arbitrary directories on the affected system. This could lead to denial of service conditions, loss of critical security logs and analysis data, disruption of malware sandboxing operations, or manipulation of the FortiSandbox environment to evade detection.

Root Cause

The root cause of this vulnerability lies in insufficient input validation and sanitization of pathname parameters in HTTP request handling. The application fails to properly restrict directory traversal sequences (such as ../ or encoded variants) in user-supplied input, allowing attackers to reference directories outside the intended scope.

When processing certain HTTP requests, the FortiSandbox CLI interface does not adequately validate that the target path remains within authorized directory boundaries. This allows an authenticated super-admin user to craft malicious requests that traverse the directory structure and target arbitrary directories for deletion.

Attack Vector

The attack is conducted over the network through crafted HTTP requests targeting the FortiSandbox management interface. An attacker must first authenticate with super-admin credentials and have CLI access to the system.

The exploitation process involves:

1. Authenticating to the FortiSandbox management interface with a super-admin account
2. Accessing the CLI functionality through the web interface
3. Crafting HTTP requests containing path traversal sequences designed to escape directory restrictions
4. Targeting specific directories for deletion through the manipulated path parameters

The vulnerability does not require user interaction and can be exploited directly by an authenticated privileged user. For technical details regarding the specific vulnerable endpoints and exploitation methods, refer to the Fortinet Security Advisory FG-IR-26-115.

Detection Methods for CVE-2026-25691

Indicators of Compromise

• Unexpected directory deletions on FortiSandbox systems, particularly system directories or analysis data folders
• Unusual HTTP request patterns in web server logs containing path traversal sequences (../, ..%2f, %2e%2e/)
• Super-admin account activity from unusual IP addresses or at unusual times
• Service disruptions or missing analysis data in FortiSandbox operations

Detection Strategies

• Monitor FortiSandbox web server access logs for HTTP requests containing directory traversal patterns in URL parameters or request bodies
• Implement file integrity monitoring on critical FortiSandbox directories to detect unauthorized deletions
• Enable comprehensive audit logging for all super-admin activities and CLI command execution
• Deploy network traffic analysis to identify anomalous HTTP request patterns targeting FortiSandbox management interfaces

Monitoring Recommendations

• Configure alerting for any deletion operations affecting system-critical directories on FortiSandbox appliances
• Establish baselines for normal super-admin activity and alert on deviations
• Monitor authentication logs for super-admin account access patterns and investigate anomalies
• Implement SIEM correlation rules to detect potential path traversal exploitation attempts

How to Mitigate CVE-2026-25691

Immediate Actions Required

• Review and restrict super-admin account access to only essential personnel
• Audit all privileged account activity on affected FortiSandbox systems for suspicious behavior
• Implement network segmentation to limit access to FortiSandbox management interfaces
• Apply vendor patches as soon as they become available from Fortinet

Patch Information

Fortinet has published security advisory FG-IR-26-115 addressing this vulnerability. Organizations should review the advisory for specific patch versions and upgrade paths for their affected FortiSandbox deployments.

Affected organizations should upgrade to patched versions of FortiSandbox as specified in the Fortinet security advisory. Contact Fortinet support or refer to FortiGuard for the latest firmware versions that address this vulnerability.

Workarounds

• Restrict network access to FortiSandbox management interfaces using firewall rules and ACLs to limit exposure
• Implement multi-factor authentication for all super-admin accounts to reduce the risk of credential compromise
• Conduct regular audits of super-admin account membership and remove unnecessary privileged access
• Consider deploying a web application firewall (WAF) in front of FortiSandbox management interfaces to filter path traversal attempts

# Example: Restrict management interface access via firewall rules
# Limit FortiSandbox management access to trusted administrator networks only
# Consult your FortiSandbox documentation for specific configuration syntax

# Review and audit super-admin accounts
# Access FortiSandbox CLI and review privileged users
# diagnose sys admin list

# Enable comprehensive audit logging
# config system global
#   set admin-audit-log enable
# end