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

What it is

A heap-based buffer overflow vulnerability in Fortinet FortiOS 7.6.0 through 7.6.3, FortiOS 7.4.0 through 7.4.8, FortiOS 7.2.0 through 7.2.11, FortiOS 7.0.0 through 7.0.17, FortiOS 6.4 all versions, FortiSwitchManager 7.2.0 through 7.2.6, FortiSwitchManager 7.0.0 through 7.0.5 allows attacker to execute unauthorized code or commands via specially crafted packets

Exploitation evidence

First exploit evidence seen: 2026-09-09 (earliest date across the sources below).

Exploited in the wild

• CISA KEV: listed since 2026-09-09. Source

Sources: CISA KEV.

How to fix it

CISA required action

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. (source: CISA KEV)

Fixed versions

• fortinet fortios: upgrade to 7.0.18 or later (affected from 6.4.0)
• fortinet fortios: upgrade to 7.2.12 or later (affected from 7.2.0)
• fortinet fortios: upgrade to 7.4.9 or later (affected from 7.4.0)
• fortinet fortios: upgrade to 7.6.4 or later (affected from 7.6.0)
• fortinet fortiswitchmanager: upgrade to 7.0.6 or later (affected from 7.0.0)
• fortinet fortiswitchmanager: upgrade to 7.2.7 or later (affected from 7.2.0)

Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.

Vendor advisories and patches

• https://fortiguard.fortinet.com/psirt/FG-IR-25-084 (CISA KEV notes)

MITRE ATT&CK mitigations for this chain

• M1050 Exploit Protection (for T1203) : Security applications that look for behavior used during exploitation such as Windows Defender Exploit Guard (WDEG) and the Enhanced Mitigation Experience Toolkit (EMET) can be used to mitigate some exploitation behavior. Control flow integrity checking is another way to potentially identify and stop a software exploi
• M1051 Update Software (for T1203) : Perform regular software updates to mitigate exploitation risk. Keeping software up-to-date with the latest security patches helps prevent adversaries from exploiting known vulnerabilities in client software, reducing the risk of successful attacks.
• M1048 Application Isolation and Sandboxing (for T1203) : Browser sandboxes can be used to mitigate some of the impact of exploitation, but sandbox escapes may still exist. Other types of virtualization and application microsegmentation may also mitigate the impact of client-side exploitation. Risks of additional exploits and weaknesses in those systems may still exist.

Detection Generic guidance

• Execution: Watch for the service process spawning shells or script interpreters (cmd.exe, powershell, sh, bash, python) via EDR process-tree rules.

Response checklist Generic guidance

1. Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
2. Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
3. Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
4. Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.