Exploited Recently addedHunt for compromise (CISA)

CVE-2026-104286

Fortinet FortiMail Path Traversal Vulnerability

9.8 Critical CVSS scoreCVSS scoreA severity score from 0 to 10, computed with an international method (CVSS). 9 or more: critical; 7 to 8.9: high; 4 to 6.9: medium. It measures the technical severity of the flaw, not the risk in your environment.

Score from the vendor or CISA, relayed by the NVD. Collected Oct 2, 2026.

Exploited sinceKEV catalogThe official list, kept by the US cybersecurity agency (CISA), of vulnerabilities that attackers are observed exploiting. A vulnerability only enters it with evidence.: October 1, 2026
RansomwareRansomwareAccording to CISA, ransomware groups (which encrypt data for ransom) use this vulnerability.: None known
CISA deadlineCISA deadlineThe remediation deadline set for US federal agencies. It does not apply elsewhere, but it is a good sense of urgency.: 3 days
CERT-FR alertCERT-FR alertCERT-FR, the incident response center of France’s ANSSI, issues an alert when a vulnerability is exploited at scale or targets France. “Active”: the alert is not closed.: None

At a glance

CISA asks you to hunt for signs of compromise: patching is not enough if the device has already been breached.

Affected product: Fortinet FortiMail (category Email, indicative classification). Name in CISA’s catalog: Fortinet FortiMail.

What should I do?

Apply the patches or mitigations from Fortinet; if none are available, stop using the product. Start with internet-facing devices.

CISA also asks you to hunt for signs of compromise: patching is not enough if the device has already been breached.

Deadline set by CISA for US federal agencies: 3 days (due October 4, 2026). It only binds those agencies, but it is a useful measure of urgency.

Fortinet security advisories page (general page, not the advisory for this vulnerability)
The vendor’s specific advisory is listed in the NVD references: CVE-2026-104286 on the NVD website.

Original text of the required action (CISA)

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.

Timeline

October 1, 2026 Vulnerability published Publication date (NVD)
October 1, 2026 Exploitation confirmed Added to CISA’s KEV catalog
October 4, 2026 CISA deadline Remediation deadline set for US federal agencies

The facts, with their sources

Each value with its source and collection date. Open for details.

Exploitation confirmed: Yes, on October 1, 2026 Date added to the catalog of exploited vulnerabilities. Exploitation itself may have started earlier. Source: KEV catalog, collected October 2, 2026 at 06:39 UTC
Ransomware: No known use to date That does not guarantee it is not being used: the information is not public. Source: KEV catalog, collected October 2, 2026 at 06:39 UTC
Hunt for compromise: Requested by CISA Source: KEV catalog, collected October 2, 2026 at 06:39 UTC
CISA required action: Apply the patches or mitigations from Fortinet; if none are available, stop using the product. Start with internet-facing devices. Rewritten by this site from CISA’s original text. Source: KEV catalog, collected October 2, 2026 at 06:39 UTC
CISA deadline: October 4, 2026, 3 days Set for US federal agencies: a measure of urgency, not an obligation elsewhere. Source: KEV catalog, collected October 2, 2026 at 06:39 UTC
Vulnerability published: October 1, 2026 Source: National Vulnerability Database (NVD), collected October 2, 2026 at 06:44 UTC
Product according to CISA: Fortinet FortiMail Filed by this site under “Email” (indicative classification). Source: KEV catalog, collected October 2, 2026 at 06:39 UTC
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Technical detail of the score: attack vector, complexity, impact. Source: National Vulnerability Database (NVD), collected October 2, 2026 at 06:44 UTC

Description

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.

Fortinet FortiMail contains a path traversal and an improper neutralization of NULL byte or NULL character vulnerability that may allow an unauthenticated attacker to write arbitrary files on the underlying system via crafted HTTP or HTTPS requests.

Summary from CISA (KEV catalog).

CERT-FR advisories

No advisory among the latest CERT-FR publications this site follows. That does not mean there are none.

Information reused under the Open Licence 2.0 (Etalab); the date of last update is shown for each advisory. This site is neither affiliated with nor endorsed by ANSSI.

Sources for this page

CISA KEV catalog: exploitation, date added, required action, deadline, ransomware.
NVD (NIST): CVSS severity, publication date, description, vendor references.
CERT-FR: advisories and alerts (in French).
Brand and category: indicative classification by this site (method).