ZeroDayAlert

CVE-2025-25249: Fortinet Multiple Products Heap-based Buffer Overflow Vulnerability

Fortinet FortiOS, FortiSwitchManager, and FortiSASE contain a heap-based buffer overflow vulnerability that allows an attacker to execute unauthorized code or commands via specially crafted packets.

Fortinet Multiple Products Added to KEV 2026-09-09 Federal due 2026-09-12 Known ransomware use

Required action — quoted from CISA

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Where this comes from. The identifier, product, dates and required action above are copied verbatim from the CISA Known Exploited Vulnerabilities catalog. The action plan below is written by an AI agent from that record and published automatically. AssurePort has not independently tested this vulnerability and makes no claim about whether any specific system is affected.

Who is affected

This vulnerability affects Fortinet FortiOS, FortiSwitchManager, and FortiSASE. It is a heap-based buffer overflow that allows remote code execution when an attacker sends specially crafted packets to an affected system. The record does not specify which versions are vulnerable, nor does it detail whether all deployment modes are equally exposed.

How to check whether this touches you

  • Inventory your Fortinet products: confirm whether you run FortiOS (on appliances or virtual instances), FortiSwitchManager, or FortiSASE anywhere in your environment.
  • Check reachability: determine whether each instance is exposed to untrusted networks, particularly the internet or guest-facing segments.
  • Retrieve the running software version on each system from the management console or CLI command output; note that version alone is not definitive proof of vulnerability or safety, as patches may be backported into older version strings.
  • Review Fortinet's advisory for your specific product and version to establish whether your configuration is in scope.

What to do

  1. Treat this as high priority: the record indicates a federal remediation deadline, and heap-based buffer overflows enable arbitrary code execution with minimal attacker skill.
  2. If you cannot patch immediately, apply network controls to limit packet ingress to known-good sources and disable any unused Fortinet services or interfaces.
  3. Enable full packet capture and alerting on traffic destined to affected systems; log all administrative access and any denied or unusual connection attempts.
  4. Obtain the vendor patch and apply it according to Fortinet's published instructions and CISA BOD 26-04 guidance for your risk profile and asset criticality; if no patch is available for your deployment, evaluate discontinuation.
  5. After patching, perform a brief validation that the system remains operational; document the patch date, version applied, and any configuration changes made during remediation.

If you find you were exposed

Exploitation of heap overflows typically occurs before public disclosure; review system logs and network traffic captures from at least the past three months for anomalous access patterns, shell spawning, or outbound connections initiated by Fortinet processes. Retention limits may constrain how far back you can search; prioritise logs from administrative interfaces and system-level audit records. If you find evidence of compromise, isolate the affected system, preserve forensic copies, and escalate to your incident response team and Fortinet support.

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This page can tell you that CVE-2025-25249 is being exploited. It cannot tell you whether Multiple Products is running somewhere of yours that is reachable. That question is what a scan answers.

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