CVE-2026-104286

Exploited in the wild. In CISA KEV since 2026‑10‑01. A vendor fix is available.

CVSS 3.19.8Critical EPSS percentile82nd2.2% chance in 30 days CISA KEVListedsince 2026-10-01, due 2026-10-04
No public exploit known FixVendor fixNo build named by the sources

Published 2026-10-01Updated 2026-10-07Sources: CVE.org, NVD

NVD CVE.org

What to do

The vendor has published a fix. Version details are below where the sources state them.

Fortinet FortiMailAffected: 8.0.0Upgrade to: not statedAffected: ≥ 7.6.0, ≤ 7.6.5Upgrade to: after 7.6.5Affected: ≥ 7.4.0, ≤ 7.4.6Upgrade to: after 7.4.6Affected: ≥ 7.2.0, ≤ 7.2.9Upgrade to: after 7.2.9 + 1 more branchStated by: CVE record

Versions as the sources state them. Full version matrix after sign-in

Steps

Written by AI from the record

Check every FortiMail appliance for its software version and whether its web interface is reachable from the internet.
Upgrade affected 8.0 systems to FortiMail 8.0.1 or above, 7.6 systems to 7.6.6 or above, 7.4 systems to 7.4.8 or above, and 7.2 systems to 7.2.10 or above, following Fortinet’s current advisory.
If an upgrade cannot be completed today, apply Fortinet’s published workaround and restrict internet access to the appliance’s web interface.
Have IT review the appliance for unexpected new or changed files and suspicious web requests after mitigation.

Some work to apply

Is your organisation exposed?Request an assessment to establish which checks fit your systems.

Coverage timeline

4 publishers

Fortinet confirmed that a critical zero-day vulnerability in FortiMail is being actively exploited in the wild, adding it to CISA's KEV catalog and providing workarounds while waiting for a fix.
as reported · Oct 2, 2026·Help Net Security summary
Fortinet issued a warning for CVE-2026-104286, a critical FortiMail vulnerability actively exploited in zero-day attacks to allow unauthenticated arbitrary file writes and code execution.
as reported · Oct 1, 2026·BleepingComputer summary
Added to CISA KEV catalog
Oct 1, 2026·CISA KEV

Sourced from public security reporting — each date is when it was published, not when it happened. 3 further articles named this CVE in wider roundups without reporting it as a distinct event.

What it is

From the CVE record

An improper limitation of a pathname to a restricted directory ('path traversal') vulnerability in Fortinet FortiMail 8.0.0 through 8.0.1, FortiMail 7.6.0 through 7.6.6, FortiMail 7.4.0 through 7.4.8, FortiMail 7.2.0 through 7.2.9 may allow an unauthenticated attacker to write arbitrary files on the underlying system via crafted HTTP or HTTPS requests.

In plain language

Written by AI from the record

FortiMail 8.0.0 through 8.0.1, 7.6.0 through 7.6.6, 7.4.0 through 7.4.8, and 7.2.0 through 7.2.9 have a critical flaw that attackers are using, so affected small businesses should act now.

Unauthenticated network-accessible path traversal in FortiMail allows crafted web requests to write or overwrite arbitrary files on the device.

If you're affected

FortiMail device takeover
Email service disruption
Malicious file placement
Sensitive email exposure
Recovery and outage costs

What is it

This flaw lets an outsider use specially formed web requests to place or replace files on a FortiMail device without permission. It is like someone being able to slip replacement documents into any locked drawer in your mailroom, potentially changing how the whole operation runs.

Who is affected

This matters if your business runs FortiMail to manage or protect email. It affects the listed FortiMail software versions and needs no attacker account or employee action. It is especially exposed when the FortiMail web service is reachable from the internet.

How urgent is it

Attackers are already exploiting this vulnerability in real attacks. CISA added it to its catalog of known exploited vulnerabilities on October 1, 2026, with a remediation deadline of October 4, 2026; treat this as an immediate priority.

What to do — in detail

Confirm the installed FortiMail release on every appliance and identify whether HTTP or HTTPS management services are exposed to untrusted networks. The vendor patch digest lists upgrade targets of FortiMail 8.0.1 or above for the 8.0 branch, 7.6.6 or above for 7.6, 7.4.8 or above for 7.4, and 7.2.10 or above for 7.2; validate the current vendor advisory before scheduling because the supplied affected-range information overlaps some listed targets. No breaking-change information is provided in the findings, so follow the vendor’s upgrade guidance and preserve configuration backups. If patching is delayed, apply the Fortinet advisory’s workaround and limit web access to trusted administrative networks. CISA’s due date is October 4, 2026. After mitigation, review FortiMail web-request logs and device storage for unexpected files or file modifications.

Technical context

Severity is CVSS 9.8 (Critical): network attack vector, low complexity, no privileges required, no user interaction, with high confidentiality, integrity, and availability impact. The weakness is CWE-22 path traversal, enabling arbitrary file write or overwrite through crafted HTTP or HTTPS requests. Exploitation is confirmed in the wild; no public exploit code is recorded. CISA KEV listing means CISA has identified this as a vulnerability known to be exploited and assigned a remediation deadline.

This is a general assessment based on public vulnerability data. It does not account for your specific infrastructure — when in doubt, consult a security specialist.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS82nd

CISA KEV

Listed as exploited in the wild since 2026-10-01.

US federal agencies must remediate by 2026-10-04.

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.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

2.2% chance of exploitation activity in the next 30 days, which ranks it in the 82nd percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Attention now

Sustained, driven by in-the-wild reports.

Lifecycle

16 events over 6 days, from the signal feeds we watch.

2026-10-07Patch availableworkaround available, record updated
2026-10-02Patch availablepatch available, workaround available, record updated, record updated
2026-10-01Added to CISA KEVpatch available, patch available, published, weakness classified, att&ck mapped, record updated, record updated

Affected products

Fortinetcommercial · USaka forti net
- FortiMailSecurity Products

And 1 more affected product. See all after sign-in

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Scored 9.8 by NVD.

How it is reached

Attack Vector NetworkExploitable remotely over the network without any special conditions
Attack Complexity LowNo special conditions — the attack can be reliably reproduced
Privileges Required NoneNo authentication required — anyone can exploit this
User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

Scope UnchangedImpact is limited to the vulnerable component itself

Impact if exploited

Confidentiality HighTotal information disclosure — all data in the component is compromised
Integrity HighTotal loss of integrity — attacker can modify any data in the component
Availability HighTotal denial of service — the component is completely unavailable