Vulnerability report

Active exploitation observed Confirmed confidence In CISA KEV

CVE-2026-104286

FortiMail Path traversal

Fortinet / FortiMail · 8.0.0

Watch CVE-2026-104286 Browse KEV feed
Severity
CVSS 9.8 · Critical
Confidence
Confirmed
Exploit status
Observed in sensors
EPSS
2.2%
First observed
05 Oct 2026
Last observed
08 Oct 2026

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2026-104286 is an unauthenticated vulnerability affecting Fortinet FortiMail. An improper limitation of a pathname to a restricted directory ('path traversal') vulnerability in Fortinet FortiMail 8.0.0 through...

Is it exploited?

Yes. Previdian sensors observed exploitation attempts with confirmed confidence. Listed in CISA KEV. Also confirmed by third-party sources.

Who is affected?

Fortinet / FortiMail 8.0.0.

What should we do?

Patch immediately, validate internet-facing exposure, and monitor for matching requests.

Overview

FortiMail Path traversal

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 Affected
FortiMail
8.0.0 Through 7.6.5 Through 7.4.6 Through 7.2.9 Through 7.0.9
Published
01 Oct 2026
Exploitation Reported
01 Oct 2026
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

edge cisa

CVE References

Exploitation evidence

Why Previdian marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

FortiGuard Center - Outbreak Alerts

Recorded 01 Oct 2026

A trusted third party reported exploitation.

Active exploitation observed

Previdian sensor

First observed 05 Oct 2026

Previdian first observed exploitation attempts targeting this vulnerability in our honeypot sensors.

Proof of concept available

GitHub

Recorded 01 Oct 2026

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

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Source Added
FortiGuard Center - Outbreak Alerts First 2026-10-01 19:38 UTC
FortiGuard 2026-10-01 19:47 UTC
CISA 2026-10-01 20:01 UTC
The Hacker News 2026-10-02 06:21 UTC
Security Affairs 2026-10-02 07:21 UTC
CERT Polska 2026-10-02 09:21 UTC
TheRegister 2026-10-02 11:20 UTC
CyberInsider 2026-10-02 18:20 UTC
SOCRadar 2026-10-04 15:21 UTC
Previdian Sensors 2026-10-06 09:47 UTC

Operational indicators for this CVE are listed under Detection.

Sensor telemetry

First-party evidence of exploitation activity

Previdian sensors recorded exploitation attempts targeting this vulnerability. The cards and chart show volume, unique attackers, and daily activity.

957

Attempts observed

3

Unique attacker IPs

2

Attacker countries

JP · PT

1

Sensors observed

CVE-2026-104286 exploitation attempts over the last 7 days

Daily events observed by Previdian sensors

Updated 10 Oct 2026

0
1
478
0
478
0
0
4 Oct 5 Oct 6 Oct 7 Oct 8 Oct 9 Oct 10 Oct

First observed 05 Oct 2026 · Last observed 08 Oct 2026

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Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
2
2
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Scanner coverage

No scanner integrations recorded yet.

Virtual patch status

Previdian virtual patch guidance is available for this CVE.

AWS WAF Cloudflare ModSecurity

Attacker IP Indicators

Attacker IP indicators observed · available in Pro and Enterprise.

Sensor-derived attacker IP indicators are available to Pro and Enterprise accounts under Detection and through the Pro API.

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Virtual Patch Detail

Compensating WAF rules for this CVE.

Available

Enterprise feature. Virtual patch rule content and deployable vendor exports (ModSecurity, Cloudflare, AWS WAF) are available to Previdian Enterprise users.

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Risk and context

Severity, weaknesses, and research context

CVSS v3.1

9.8 Critical

Potential damage if exploited. Separate from whether attackers are using it.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P/RL:O/RC:C

EPSS

2.2%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') CWE-22

Recent mention · CyberInsider

FortiMail zero-day exploited in attacks as CISA urges immediate patching

A critical zero-day vulnerability in Fortinet FortiMail is being actively exploited in the wild, prompting the US Cybersecurity and Infrastructure Security Agency (CISA) to add the flaw to its Known Exploited Vulnerabilities (KEV) catalog. Tracked as CVE-2026-104286 and rated...

Read full advisory

All Mentions

Recent mention · CyberInsider

FortiMail zero-day exploited in attacks as CISA urges immediate patching

CyberInsider · 02 Oct 2026

A critical zero-day vulnerability in Fortinet FortiMail is being actively exploited in the wild, prompting the US Cybersecurity and Infrastructure Security Agency (CISA) to add the flaw to its Known Exploited Vulnerabilities (KEV) catalog. Tracked as CVE-2026-104286 and rated 9.8 (Critical) on the CVSS scale, the vulnerability allows unauthenticated attackers to write arbitrary files to … The post FortiMail zero-day exploited in attacks as CISA urges immediate patching appeared first on CyberInsider.

Recent mention · SOCRadar

FortiMail Zero-Day Under Active Exploitation

SOCRadar · 02 Oct 2026

FortiMail Zero-Day Under Active Exploitation Fortinet has confirmed that CVE-2026-104286, a critical path traversal flaw in FortiMail, is being exploited in zero-day attacks, and CISA added it to the Known Exploited Vulnerabilities (KEV) catalog on the same day the advisory went live. Fixed builds are not yet available for most affected branches, so the primary […]

Recent mention · TheRegister

Fortinet sounds the alarm over actively exploited FortiMail zero-day

TheRegister · 02 Oct 2026

No login required, exploitation underway, and some admins are still waiting for patches

Recent mention · CERT Polska

Krytyczna podatność w FortiMail aktywnie wykorzystywana w atakach

CERT Polska · 02 Oct 2026

Zespół CERT Polska informuje o krytycznej podatności w FortiMail.Podatność, oznaczona jako CVE-2026-104286, umożliwia nieuwierzytelnionemu atakującemu zapisywanie dowolnych plików w systemie i w konsekwencji wykonanie dowolnego kodu, poprzez specjalnie sformatowane żądania HTTP. Wykorzystanie podatności wymaga dostępu do interfejsu zarządzania FortiMail. Producent potwierdza, że luka jest aktywnie wykorzystywana w atakach.Podatność dotyczy następujących wersji:FortiMail 8.0: 8.0.0 - 8.0.1FortiMail 7.6: 7.6.0 - 7.6.6FortiMail 7.4: 7.4.0 - 7.4.8FortiMail 7.2: 7.2.0 - 7.2.9Na moment publikacji...

Recent mention · NCSC Security Advisories

NCSC-2026-0398 [1.00] [M/H] Kwetsbaarheid verholpen in Fortinet FortiMail

NCSC Security Advisories · 02 Oct 2026

Fortinet heeft een kwetsbaarheid verholpen in FortiMail. FortiMail bevat een kritieke kwetsbaarheid (CVE-2026-104286) in de verwerking van bestandspaden, veroorzaakt door een combinatie van Path Traversal (CWE-22) en onvoldoende neutralisatie van NULL-bytes (CWE-158). Een niet-geauthenticeerde aanvaller kan via speciaal vervaardigde HTTP- of HTTPS-verzoeken willekeurige bestanden op het onderliggende systeem schrijven. De kwetsbaarheid wordt actief geëxploiteerd. Getroffen zijn FortiMail 7.2.0–7.2.9, 7.4.0–7.4.8, 7.6.0–7.6.6 en 8.0.0–8.0.1 waarbij de functionaliteit IBE (Identity Based...

Recent mention · Security Affairs

U.S. CISA adds Fortinet FortiMail flaw to its Known Exploited Vulnerabilities catalog

Security Affairs · 02 Oct 2026

U.S. Cybersecurity and Infrastructure Security Agency (CISA) adds Fortinet FortiMail flaw to its Known Exploited Vulnerabilities catalog. The U.S. Cybersecurity and Infrastructure Security Agency (CISA) added a Fortinet FortiMail flaw, tracked as CVE-2026-104286 (CVSS score of 9.8), to its Known Exploited Vulnerabilities (KEV) catalog. The flaw is a path traversal vulnerability that can be triggered through […]

Recent mention · The Hacker News

Critical FortiMail Zero-Day Flaw Exploited in Attacks Allows Unauthenticated Arbitrary File Writes

The Hacker News · 02 Oct 2026

The U.S. Cybersecurity and Infrastructure Security Agency (CISA), on Thursday, added a critical security flaw impacting Fortinet FortiMail to its Known Exploited Vulnerabilities (KEV) catalog, following reports of active exploitation. The vulnerability, tracked as CVE-2026-104286 (CVSS score: 9.8), allows unauthenticated attackers to write arbitrary files on the underlying system. "An improper

Recent mention · FortiGuard

Improper limitation of a pathname to a restricted directory

FortiGuard · 01 Oct 2026

CVSSv3 Score: 9.8 An Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') [CWE-22] and Improper Neutralization of NULL Byte or NULL Character [CWE-158] vulnerability may allow an unauthenticated attacker to write arbitrary files on the underlying system via crafted HTTP or HTTPS requests.This has been reported to be exploited in the wild, customers are urged to apply the workaround below. Revised on 2026-10-01 00:00:00

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

ShadowForge-Cyber/CVE-2026-104286-POC

github · Created 2026-10-01 22:15:42 UTC · 0 stars · AI assessment 85%

Timeline

From disclosure to observed exploitation

  1. 16:43 UTC

    Virtual patch available

    Compensating WAF rule available to block exploitation

  2. 22:22 UTC

    Indicators of compromise added (3)

    Indicators of compromise recorded

  3. 22:22 UTC

    Observed by Previdian sensors

    Evidence-backed exploitation signal

  4. 15:21 UTC

    KEV confirmed by SOCRadar

    Exploitation attested by an external source

  5. 18:20 UTC

    KEV confirmed by CyberInsider

    Exploitation attested by an external source

  6. 11:20 UTC

    KEV confirmed by TheRegister

    Exploitation attested by an external source

  7. 09:21 UTC

    KEV confirmed by CERT Polska

    Exploitation attested by an external source

  8. 07:21 UTC

    KEV confirmed by Security Affairs

    Exploitation attested by an external source

  9. 06:21 UTC

    KEV confirmed by The Hacker News

    Exploitation attested by an external source

  10. 22:15 UTC

    Public PoC available

    Public proof-of-concept code published

  11. 20:01 UTC

    Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  12. 19:47 UTC

    KEV confirmed by FortiGuard

    Exploitation attested by an external source

  13. 19:38 UTC

    Added to Previdian KEV Feed

    High-confidence, third-party attested exploitation

  14. 19:17 UTC

    CVE published

    Vulnerability disclosed publicly

  15. 19:12 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
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  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2026-104286

Free JSON includes basic KEV fields 
{
  "cve_id": "CVE-2026-104286",
  "confidence": "Confirmed",
  "cvss_score": 9.8,
  "cvss_estimated": false,
  "epss_score": 0.02201,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": true
  },
  "sensor_telemetry": { "attempts": 957, "sensors": 1 }
}