CVE-2025-54820: Fortinet FortiManager Buffer Overflow

CVE-2025-54820 Overview

A Stack-based Buffer Overflow vulnerability (CWE-121) has been identified in Fortinet FortiManager, a centralized management solution for Fortinet network devices. This vulnerability may allow a remote unauthenticated attacker to execute unauthorized commands via crafted requests when the vulnerable service is enabled. The success of the attack depends on the ability to bypass stack protection mechanisms.

Critical Impact

Remote unauthenticated attackers could potentially execute unauthorized commands on affected FortiManager instances, compromising the integrity of centralized network management infrastructure.

Affected Products

• Fortinet FortiManager 7.4.0 through 7.4.2
• Fortinet FortiManager 7.2.0 through 7.2.10
• Fortinet FortiManager 6.4 all versions

Discovery Timeline

• 2026-03-10 - CVE-2025-54820 published to NVD
• 2026-03-12 - Last updated in NVD database

Technical Details for CVE-2025-54820

Vulnerability Analysis

This vulnerability represents a classic stack-based buffer overflow condition where insufficient bounds checking allows an attacker to write beyond the allocated buffer on the stack. FortiManager processes incoming network requests, and certain input fields are not properly validated for length before being copied to fixed-size stack buffers.

The vulnerability is classified under both CWE-121 (Stack-based Buffer Overflow) and CWE-787 (Out-of-bounds Write), indicating that the flaw involves writing data beyond the boundaries of allocated memory on the stack. This type of vulnerability can lead to corruption of adjacent stack data, including return addresses and saved registers.

While the attack complexity is high due to the requirement to bypass stack protection mechanisms such as stack canaries and ASLR, successful exploitation could result in complete compromise of confidentiality, integrity, and availability of the affected system.

Root Cause

The root cause lies in improper input validation where user-supplied data from network requests is copied to stack-allocated buffers without adequate length verification. When the input exceeds the expected buffer size, it overwrites adjacent memory regions on the stack, potentially including function return addresses and other control flow data.

Attack Vector

The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker can send specially crafted requests to the vulnerable FortiManager service. The crafted payload must be designed to:

1. Overflow the vulnerable stack buffer with attacker-controlled data
2. Bypass stack protection mechanisms (stack canaries, ASLR)
3. Redirect execution flow to achieve command execution

The attack mechanism involves sending malformed requests with oversized input fields that overflow stack-allocated buffers. Successful exploitation requires bypassing modern stack protection mechanisms, which increases the complexity of a successful attack. For detailed technical information, refer to the FortiGuard Security Advisory.

Detection Methods for CVE-2025-54820

Indicators of Compromise

• Unusual network traffic patterns targeting FortiManager management interfaces with abnormally large request payloads
• Unexpected service crashes or restarts of FortiManager processes that may indicate exploitation attempts
• Anomalous process execution or commands spawned from FortiManager service processes
• Evidence of stack smashing or memory corruption in system logs

Detection Strategies

• Deploy network intrusion detection signatures to identify malformed requests targeting FortiManager services
• Monitor FortiManager application logs for service crashes, segmentation faults, or unexpected terminations
• Implement deep packet inspection to detect requests with oversized or malformed input fields
• Establish behavioral baselines for FortiManager network traffic and alert on deviations

Monitoring Recommendations

• Enable verbose logging on FortiManager instances to capture detailed request information
• Configure SIEM alerts for repeated connection attempts with large payloads to FortiManager management ports
• Monitor system resource usage for signs of memory corruption or abnormal process behavior
• Implement network segmentation to restrict access to FortiManager management interfaces

How to Mitigate CVE-2025-54820

Immediate Actions Required

• Review the FortiGuard Security Advisory FG-IR-26-098 for official guidance and patch availability
• Restrict network access to FortiManager management interfaces to trusted networks only
• Implement firewall rules to limit exposure of FortiManager services to the internet
• Review and disable unnecessary services on FortiManager instances

Patch Information

Fortinet has published a security advisory addressing this vulnerability. Organizations should consult the FortiGuard Security Advisory for specific patch versions and upgrade guidance. Ensure FortiManager installations are updated to patched versions as soon as they become available.

Workarounds

• Implement strict network access controls to limit which hosts can communicate with FortiManager management interfaces
• Place FortiManager instances behind a web application firewall (WAF) configured to filter malicious payloads
• If the vulnerable service can be identified, consider disabling it until a patch is applied if operationally feasible
• Enable additional monitoring and logging to detect potential exploitation attempts

# Example: Restrict FortiManager access to trusted management networks
# Configure firewall rules to limit access to management interfaces
iptables -A INPUT -p tcp --dport 443 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP