Overview
A high-severity vulnerability, identified as CVE-2025-53843, affects multiple versions of Fortinet FortiOS. This stack-based buffer overflow vulnerability could allow a remote attacker to execute unauthorized code or commands on a vulnerable system by sending specially crafted packets. This poses a significant risk to organizations using affected FortiOS versions.
Technical Details
CVE-2025-53843 is a stack-based buffer overflow. Specifically, a weakness in how FortiOS handles certain incoming network packets creates an opportunity for an attacker to overwrite parts of the system’s memory. By sending carefully constructed packets, an attacker can potentially inject and execute malicious code. The exact attack vector and vulnerable components within FortiOS are detailed in the Fortinet advisory referenced below.
CVSS Analysis
The Common Vulnerability Scoring System (CVSS) has assigned a score of 7.5 to CVE-2025-53843, indicating a HIGH severity. This score reflects the potential for a remote, unauthenticated attacker to compromise the confidentiality, integrity, and availability of the affected system.
Possible Impact
Successful exploitation of CVE-2025-53843 could lead to:
- Remote code execution, allowing an attacker to gain complete control of the affected FortiOS device.
- Data breach due to unauthorized access to sensitive information.
- Denial of service (DoS) attacks, disrupting network services.
- Compromise of network security policies and firewalls.
Mitigation or Patch Steps
Fortinet has released patches to address CVE-2025-53843. It is strongly recommended that users of the following FortiOS versions upgrade to a patched version as soon as possible:
- FortiOS 7.6.0 through 7.6.3: Upgrade to a fixed version (check Fortinet advisory for the specific fixed version).
- FortiOS 7.4.0 through 7.4.8: Upgrade to a fixed version (check Fortinet advisory for the specific fixed version).
- FortiOS 7.2 all versions: Upgrade to a supported and patched version.
- FortiOS 7.0 all versions: Upgrade to a supported and patched version.
- FortiOS 6.4 all versions: Upgrade to a supported and patched version.
If immediate patching is not possible, consider implementing temporary workarounds, such as network segmentation and restricting access to vulnerable services. Consult the Fortinet advisory for specific workaround recommendations.
