CVE-2025-58413: Fortinet FortiOS Buffer Overflow Flaw

CVE-2025-58413 Overview

CVE-2025-58413 is a stack-based buffer overflow vulnerability affecting multiple versions of Fortinet FortiOS and FortiSASE. The flaw allows an attacker on an adjacent network to execute unauthorized code or commands by sending specially crafted packets to a vulnerable device. The vulnerability is tracked under [CWE-121] (Stack-based Buffer Overflow) and [CWE-787] (Out-of-bounds Write). Fortinet published security advisory FG-IR-25-632 covering this issue.

Critical Impact

Successful exploitation can result in unauthorized code execution on affected FortiOS and FortiSASE devices, compromising confidentiality, integrity, and availability of the perimeter security appliance.

Affected Products

• Fortinet FortiOS 7.6.0 through 7.6.3, 7.4.0 through 7.4.8, all versions of 7.2, 7.0, 6.4, 6.2, and 6.0
• Fortinet FortiSASE 25.3.b
• Fortinet FortiSASE 25.3.89 (feature and mature branches)

Discovery Timeline

• 2025-11-18 - CVE-2025-58413 published to NVD
• 2025-11-21 - Last updated in NVD database

Technical Details for CVE-2025-58413

Vulnerability Analysis

The vulnerability is a stack-based buffer overflow in packet processing logic within FortiOS and FortiSASE. An attacker on the same network segment as a vulnerable device can craft malformed packets that exceed expected size boundaries during parsing. When the device copies attacker-controlled data into a fixed-size stack buffer without proper length validation, adjacent stack memory is overwritten. This corruption can override the saved return address or other control structures on the stack, enabling arbitrary code execution in the context of the affected service.

Fortinet has not publicly disclosed the specific protocol handler or daemon containing the flaw. The advisory FG-IR-25-632 should be consulted for vendor-confirmed technical details.

Root Cause

The root cause is improper bounds checking when copying data from network input into a fixed-size stack buffer. The condition aligns with [CWE-121] and [CWE-787], where a write operation extends beyond the intended memory region. Attacker-controlled bytes overwrite saved registers and the return address, allowing redirection of execution flow.

Attack Vector

Exploitation requires adjacent network access, meaning the attacker must be positioned on the same logical or physical network segment as the target device. No authentication or user interaction is required. The attack complexity is elevated because the attacker must reliably control buffer contents and bypass any memory protection mechanisms present on FortiOS appliances. There are no publicly available proof-of-concept exploits at the time of writing, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

No verified public exploit code is available. Refer to the Fortinet Security Advisory FG-IR-25-632 for vendor-supplied details.

Detection Methods for CVE-2025-58413

Indicators of Compromise

• Unexpected crashes, reboots, or crashlog entries on FortiOS or FortiSASE devices coinciding with anomalous network traffic
• Malformed or oversized packets from adjacent network hosts directed at management or service interfaces
• Unusual outbound connections originating from the Fortinet appliance after suspicious inbound traffic

Detection Strategies

• Inspect FortiOS diagnose debug crashlog output for repeated faults in network-facing daemons
• Deploy IDS/IPS signatures that flag malformed packet structures targeting Fortinet management protocols on adjacent segments
• Correlate network telemetry with appliance event logs to identify packet floods or protocol anomalies preceding device instability

Monitoring Recommendations

• Forward FortiOS syslog and crash data to a centralized SIEM for continuous review
• Monitor adjacent network segments for unauthorized devices that could launch local-network attacks
• Track FortiGuard PSIRT advisories and subscribe to vendor notification channels for advisory FG-IR-25-632 updates

How to Mitigate CVE-2025-58413

Immediate Actions Required

• Identify all FortiOS and FortiSASE deployments and confirm version against the affected ranges
• Apply Fortinet-supplied patches for FortiOS 7.6.x and 7.4.x branches as referenced in advisory FG-IR-25-632
• Plan upgrade paths for end-of-support branches 7.2, 7.0, 6.4, 6.2, and 6.0 to a supported, patched release

Patch Information

Fortinet has published remediation guidance in Fortinet Security Advisory FG-IR-25-632. Administrators should consult the advisory for the specific fixed versions corresponding to each affected branch and upgrade accordingly.

Workarounds

• Restrict access to FortiOS management and service interfaces to trusted administrative VLANs only
• Segment the network so that untrusted hosts cannot reach the appliance over adjacent Layer 2 paths
• Disable any non-essential services on FortiOS devices to reduce the network-facing attack surface until patches are applied

# Example: restrict admin access to a trusted subnet on FortiOS
config system interface
  edit "port1"
    set allowaccess ping https ssh
    set trust-ip-1 10.0.0.0 255.255.255.0
  next
end