CVE-2025-53843: 
FortiOS Schwachstellenanalyse und -minderung

CVE-2025-53843 is a stack-based buffer overflow vulnerability discovered in the CAPWAP daemon of Fortinet FortiOS. The vulnerability affects multiple versions including FortiOS 7.6.0 through 7.6.3, FortiOS 7.4.0 through 7.4.8, and all versions of FortiOS 7.2, 7.0, and 6.4. Initially disclosed on November 18, 2025, this vulnerability was internally discovered by Gwendal Guégniaud of Fortinet Product Security Team (Fortinet Advisory, NVD).

The vulnerability is classified as a stack-based buffer overflow (CWE-124) in the CAPWAP daemon. It allows a remote authenticated attacker to execute arbitrary code or commands as a low privileged user through specially crafted packets. The vulnerability has been assigned a CVSSv3.1 score of 6.9 (Medium severity). Successful exploitation requires significant preparation due to stack protection and ASLR (Address Space Layout Randomization) security measures. Additionally, the attacker must be able to pose as an authorized FortiAP or FortiExtender (Fortinet Advisory).

If successfully exploited, the vulnerability allows attackers to execute unauthorized code or commands with low-level privileges. The impact is particularly concerning in environments where FortiAP or FortiExtender devices are deployed. When auto-auth-extension-device is enabled in the system interface configuration, the vulnerability can be exploited without administrator authorization, though this feature is disabled by default (Fortinet Advisory, CIS Advisory).

Fortinet has released patches and recommends upgrading to FortiOS version 7.6.4 or above for 7.6.x installations, and 7.4.9 or above for 7.4.x installations. Users of FortiOS 7.2, 7.0, and 6.4 versions should migrate to a fixed release. Temporary workarounds include disabling security fabric access into interface and only allowing legitimate devices in Wifi Controller > Managed FortiAPs. It's crucial to ensure that auto-auth-extension-device is disabled in the system interface configuration (Fortinet Advisory).