CVE-2026-22627: FortiSwitchAXFixed Buffer Overflow Flaw

CVE-2026-22627 Overview

A classic buffer overflow vulnerability (CWE-120) has been identified in Fortinet FortiSwitchAXFixed versions 1.0.0 through 1.0.1. This buffer copy without checking size of input vulnerability allows an unauthenticated attacker within the same adjacent network to execute unauthorized code or commands on the device by sending a crafted LLDP (Link Layer Discovery Protocol) packet.

Critical Impact

Unauthenticated attackers on an adjacent network can achieve remote code execution on vulnerable FortiSwitchAXFixed devices via malicious LLDP packets, potentially leading to complete device compromise.

Affected Products

• Fortinet FortiSwitchAXFixed version 1.0.0
• Fortinet FortiSwitchAXFixed version 1.0.1

Discovery Timeline

• 2026-03-10 - CVE-2026-22627 published to NVD
• 2026-03-11 - Last updated in NVD database

Technical Details for CVE-2026-22627

Vulnerability Analysis

This vulnerability stems from a classic buffer overflow condition (CWE-120) in the LLDP packet processing functionality of FortiSwitchAXFixed devices. When the device receives LLDP packets, it copies input data into a fixed-size buffer without properly validating the size of the incoming data. This lack of bounds checking allows an attacker to overflow the buffer, potentially overwriting adjacent memory regions.

The attack requires the adversary to be on the same adjacent network as the vulnerable device, meaning they must have Layer 2 network access. No authentication or user interaction is required to exploit this vulnerability, making it particularly dangerous in shared network environments.

Root Cause

The root cause is improper input validation during LLDP packet processing. The affected FortiSwitchAXFixed versions fail to verify that incoming LLDP packet data fits within the allocated buffer space before performing the copy operation. This is a classic example of CWE-120 (Buffer Copy without Checking Size of Input), where the absence of boundary checks enables memory corruption.

Attack Vector

The attack is conducted over the adjacent network (Layer 2), requiring the attacker to have direct network access to the same broadcast domain as the vulnerable switch. The attacker crafts a malicious LLDP packet with oversized data fields and sends it to the target FortiSwitchAXFixed device. When the device processes the packet, the buffer overflow occurs, allowing the attacker to potentially:

• Execute arbitrary code on the device
• Run unauthorized commands with device-level privileges
• Cause denial of service conditions
• Compromise the integrity and confidentiality of data traversing the switch

The vulnerability can be exploited by sending specially crafted LLDP packets to the target device. LLDP operates at Layer 2 and is commonly used for network topology discovery. Attackers with adjacent network access can craft packets with malformed TLV (Type-Length-Value) fields that exceed expected buffer sizes, triggering the overflow condition. For complete technical details, refer to the Fortinet Security Advisory FG-IR-26-086.

Detection Methods for CVE-2026-22627

Indicators of Compromise

• Abnormally large or malformed LLDP packets on the network targeting FortiSwitchAXFixed devices
• Unexpected device crashes, reboots, or unstable behavior on FortiSwitchAXFixed appliances
• Suspicious command execution or process anomalies on affected switches
• Unusual outbound network connections from the switch management interface

Detection Strategies

• Monitor for anomalous LLDP traffic patterns, particularly packets with unusually large TLV fields
• Implement network intrusion detection signatures for malformed LLDP packets targeting FortiSwitch devices
• Deploy packet capture and analysis on network segments containing FortiSwitchAXFixed devices
• Enable enhanced logging on FortiSwitchAXFixed devices to capture packet processing errors

Monitoring Recommendations

• Configure SIEM alerts for LLDP-related anomalies on network segments with affected FortiSwitch devices
• Monitor device health metrics including CPU utilization, memory usage, and crash reports
• Implement network segmentation monitoring to detect unauthorized adjacent network access
• Review device logs for buffer overflow or memory corruption error messages

How to Mitigate CVE-2026-22627

Immediate Actions Required

• Identify all FortiSwitchAXFixed devices running versions 1.0.0 through 1.0.1 in your environment
• Apply the security patch from Fortinet as soon as available per the Fortinet Security Advisory FG-IR-26-086
• Implement network segmentation to restrict adjacent network access to FortiSwitchAXFixed devices
• Consider disabling LLDP on affected devices if not required for network operations

Patch Information

Fortinet has released information regarding this vulnerability in security advisory FG-IR-26-086. Organizations should consult the Fortinet Security Advisory FG-IR-26-086 for the latest patch availability and upgrade instructions. Upgrade FortiSwitchAXFixed to a patched version as recommended by Fortinet.

Workarounds

• Disable LLDP functionality on FortiSwitchAXFixed devices if it is not essential for network operations
• Implement strict network access controls to limit which devices can communicate on the same Layer 2 segment
• Deploy network access control (NAC) solutions to prevent unauthorized devices from joining the network
• Monitor and filter LLDP traffic using upstream network security devices where possible

# Example: Verify FortiSwitchAXFixed version and check LLDP status
# Consult Fortinet documentation for specific CLI commands
# Check current firmware version
get system status

# Review LLDP configuration
show switch lldp status