10 September 2026
Reference: CVE-2025-25249
1. What is being reported?
A technical flaw called a 'heap-based buffer overflow' affects several versions of Fortinet's FortiOS and FortiSwitchManager products. This flaw allows attackers to send specially crafted data packets that can let them run unauthorised commands or code on the affected devices.
2. What this means in plain English
If your organisation uses Fortinet devices to manage or protect your network, attackers could exploit this flaw to take control of those devices. This could lead to loss of data, disruption of services, or attackers using your network to reach other systems.
3. Could this affect a small business?
Small businesses that use Fortinet products listed in the affected versions could be at risk, especially if those devices are connected to the internet. Organisations not using these products or using versions outside the affected range are less likely to be affected.
4. What to do now
- Check if your organisation uses any Fortinet FortiOS or FortiSwitchManager products in the affected versions.
- Contact your IT provider or Fortinet support to confirm if your devices are vulnerable and to get instructions on applying security updates or mitigations.
- Apply all recommended patches or mitigations promptly to protect your network from known attacks.
- Review your network exposure and consider limiting internet access to these devices if immediate patching is not possible.
5. Ask your IT provider
Can you confirm whether our Fortinet devices are affected by CVE-2025-25249 and what steps are being taken to apply the necessary security updates or mitigations?
6. Bottom line
If you use Fortinet network products, act quickly to update or secure them to prevent attackers from exploiting this serious vulnerability.
Information based on CISA KEV, NVD, and reputable security reporting.