Introduction
An SQL injection vulnerability in the FortiDDoS-F REST API gives authenticated attackers a direct path to executing arbitrary SQL commands against the appliance's backend database. For organizations relying on FortiDDoS-F to protect against volumetric and application layer DDoS attacks, this flaw undermines the integrity of the very device tasked with defending their network perimeter.
FortiDDoS-F is Fortinet's dedicated DDoS mitigation appliance, designed to detect and block DDoS attacks at the network edge using behavioral analysis rather than signature based detection. It is deployed by enterprises and service providers to protect critical infrastructure, and its REST API serves as the primary programmatic management interface for configuration, monitoring, and automation workflows.
Technical Information
The root cause of CVE-2026-39815 is an improper neutralization of special elements used in SQL commands, classified under CWE-89 (SQL Injection). The vulnerable component is the REST API of the FortiDDoS-F appliance.
The FortiDDoS REST API is a powerful management interface that allows administrators to configure settings, gather statistics, and manage the appliance using standard HTTP methods. The API supports JSON for settings data and XML for traffic graph information, and authenticates requests using bearer tokens. Its capabilities include modifying service protection profiles, retrieving system statistics, and downloading backup configuration files.
The flaw exists because the API does not properly sanitize or parameterize user supplied input before incorporating it into SQL queries. When an authenticated user sends a crafted HTTP request containing malicious SQL fragments, those fragments pass through to the database engine without adequate neutralization.
Attack Flow
The exploitation of this vulnerability follows a clear sequence:
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Authentication: The attacker must first obtain valid credentials and authenticate to the FortiDDoS-F system. The REST API uses bearer token authentication, so the attacker needs a valid token, which is obtained through the standard API login flow.
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Crafted API Request: With a valid bearer token, the attacker constructs an HTTP request to the REST API that embeds SQL injection payloads within request parameters or body fields. The specific API endpoint or parameter that is vulnerable has not been publicly disclosed by Fortinet.
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SQL Execution: Because the API fails to neutralize special characters (such as single quotes, semicolons, or SQL keywords) in the input, the injected SQL is concatenated into the query string and executed by the database engine.
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Impact: Successful exploitation allows the attacker to run arbitrary SQL queries. Given the API's extensive control over the appliance, this could result in exfiltration of sensitive configuration data, modification of protection profiles, or broader compromise of the appliance's operational integrity.
The CVSS score assigned by FortiGuard Labs is 7.9 (High), while the NVD lists a score of 8.8. The requirement for prior authentication is a meaningful barrier to exploitation, but it does not eliminate the risk. Credential theft, insider threats, or compromised service accounts with API access could all provide the necessary foothold.
Affected Systems and Versions
The following versions of FortiDDoS-F are affected:
| Product | Vulnerable Versions | Fixed Version |
|---|---|---|
| FortiDDoS-F | 7.2.1 through 7.2.2 | 7.2.3 or above |
The following FortiDDoS-F versions are explicitly not affected:
- FortiDDoS-F 7.0 (all releases)
- FortiDDoS-F 6.6 (all releases)
- FortiDDoS-F 6.5 (all releases)
- FortiDDoS-F 6.4 (all releases)
- FortiDDoS-F 6.3 (all releases)
Only systems where the REST API is enabled and accessible are exposed to this vulnerability. Environments where API access has been disabled or restricted to trusted management networks have a reduced attack surface.
Vendor Security History
Fortinet has a well documented history of critical vulnerabilities in its perimeter security products that have been widely exploited by threat actors:
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CVE-2018-13379: A path traversal vulnerability in Fortinet SSL VPNs that was routinely exploited by multiple threat actors, including the LockBit ransomware group, across several years. This vulnerability appeared in CISA's 2022 list of top routinely exploited vulnerabilities.
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CVE-2022-40684: An authentication bypass vulnerability in FortiOS and FortiProxy that was added to the CISA Known Exploited Vulnerabilities catalog and required urgent mitigation across affected organizations.
This pattern demonstrates that Fortinet appliances, particularly those exposed at the network perimeter, are consistently targeted by sophisticated threat actors. Patches for Fortinet products should be treated with high priority in any vulnerability management program.
References
- FortiGuard PSIRT Advisory FG-IR-26-119
- FortiDDoS-F 7.0.3 Handbook
- FortiDDoS REST API Reference
- CISA: 2022 Top Routinely Exploited Vulnerabilities
- CISA: Understanding LockBit
- Fortinet Blog: Update Regarding CVE-2022-40684
- CISA Known Exploited Vulnerabilities Catalog (Fortinet)
- Fortinet Q4 2025 Financial Results
