CVE-2025-25249 · High · CISA KEV

Fortinet Heap Buffer Overflow (CVE-2025-25249) Actively Exploited in the Wild

Threat Engine Auto-Feed · data current as of 2026-09-10

A heap-based buffer overflow in multiple Fortinet products (FortiOS, FortiSwitchManager, FortiSASE) allows for unauthorized code execution via specially crafted packets. This vulnerability is actively exploited in the wild, as confirmed by its inclusion in CISA's KEV catalog, indicating a high likelihood of successful exploitation.

  • CVSS:
  • EPSS percentile: 0.75786
  • Exploitation pressure: 70/100 (High)

Exploitation reality: listed in CISA KEV (exploited in the wild) · EPSS 76th percentile. Threat × Vulnerability from public signals — impact depends on your environment.

Weakness —

A heap-based buffer overflow occurs when a program writes more data to a memory buffer than it was designed to hold, specifically in the 'heap' memory region. This can overwrite adjacent memory, leading to crashes, unpredictable behavior, or, critically, allowing an attacker to inject and execute their own malicious code or commands.

Who's at risk

Exposure: unknown · Auth: unknown · unknown

Enterprise profiles most at risk

  • Organizations using Fortinet FortiOS, FortiSwitchManager, or FortiSASE products
  • Financial services organizations (targeted by FIN7, LockBit affiliates, APT38)
  • Technology sector organizations (targeted by APT29, Scattered Spider)

Misconfigurations that escalate it

  • Lack of network segmentation, allowing crafted packets to reach vulnerable devices
  • Insufficient monitoring of network traffic for anomalous packet structures

High-impact scenarios

  • Remote code execution on critical network infrastructure devices
  • Unauthorized command execution, leading to system compromise
  • Potential for network-wide impact if exploited devices manage other systems or provide critical services

Likely adversaries

  • FIN7 — Financial services (Assessed)
  • LockBit affiliates — Financial services (Assessed)
  • APT38 (Lazarus) — Financial services (Assessed)
  • APT29 (Cozy Bear) — Technology (Assessed)
  • Scattered Spider — Technology (Assessed)

What to do (defensive)

Detect

  • Monitor network traffic for unusual or malformed packets targeting Fortinet devices
  • Review Fortinet device logs for signs of crashes, unexpected reboots, or unauthorized command execution
  • Implement network intrusion detection systems (NIDS) to flag suspicious packet patterns

Contain

  • Isolate affected Fortinet devices from critical network segments if immediate patching is not feasible
  • Implement strict access controls to Fortinet management interfaces
  • Block traffic from known malicious IP addresses or suspicious sources

Patch

  • Apply vendor-provided security patches for Fortinet FortiOS, FortiSwitchManager, and FortiSASE as soon as they become available

Frontier verdict — High

This is a high-priority vulnerability due to active exploitation in the wild (CISA KEV) and its potential for remote code execution on critical network infrastructure.

For detection-engineering and awareness only · point-in-time · not security advice · sourced from NVD, FIRST EPSS, CISA KEV. Adversary mappings are assessments unless cited.