# CVE-2026-126163: Fortinet FortiMail format string in SMTP

Source: https://junglewise.ai/threats/cve-2026-126163-a-use-of-externally-controlled-format-string-vulnerability-in  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-11. Updated: 2026-11-11  
License: CC BY 4.0 with a link back

CVE-2026-126163 · Severity: high · CVSS 8.1 · Published 2026-11-11

FortiMail is an email security gateway that filters and protects corporate email. A format string vulnerability in its SMTP command processor allows a remote attacker without authentication to execute arbitrary code on the system, potentially leading to full system compromise and access to all email data.

Technologies: [Fortinet FortiMail](https://junglewise.ai/threats/technologies/fortimail). Vendors: [Fortinet](https://junglewise.ai/threats/vendors/fortinet).

## Quick answers

**Is CVE-2026-126163 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-126163 being exploited in the wild.

**How severe is CVE-2026-126163?** High severity, with a CVSS score of 8.1, published 11 November 2026.

**Which products and versions are affected?** Fortinet FortiMail 8.0.0 through 8.0.1.

**Is there a fix for CVE-2026-126163?** Yes: fixed in FortiMail 8.0.2 and above. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-126163 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-126163?** Check whether you run Fortinet FortiMail at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in FortiMail 8.0.2 and above

## Technical details

A use-after-free or format string vulnerability exists in the SMTP API component (CWE-134) of FortiMail 8.0.0 and 8.0.1. An unauthenticated remote attacker can trigger code execution by sending a specially crafted SMTP command that exploits improper handling of format string input. The attack requires no authentication or user interaction, making it highly exploitable.

## Affected products

- Fortinet FortiMail 8.0.0 through 8.0.1

## Timeline

- 2026-11-10: disclosed
- 2026-10-05: patched: FortiMail Cloud updated to v7.6.7 GA or v8.0.2 GA

## References

- [https://fortiguard.fortinet.com/psirt/FG-IR-26-215](https://fortiguard.fortinet.com/psirt/FG-IR-26-215)

## Related threats

- [Fortinet FortiMail SQL injection](https://junglewise.ai/threats/cve-2026-126263-a-improper-neutralization-of-special-elements-used-in-an-sql)
- [Fortinet FortiMail argument injection in administrative interface](https://junglewise.ai/threats/cve-2026-126169-a-improper-neutralization-of-argument-delimiters-in-a-command)
- [Fortinet FortiMail argument injection in administrative interface](https://junglewise.ai/threats/cve-2026-126168-a-improper-neutralization-of-argument-delimiters-in-a-command)
- [Fortinet FortiMail command injection in admin GUI](https://junglewise.ai/threats/cve-2026-126167-a-improper-neutralization-of-special-elements-used-in-a-command)
- [Fortinet FortiMail argument injection in admin interface](https://junglewise.ai/threats/cve-2026-126166-a-improper-neutralization-of-argument-delimiters-in-a-command)