Fortinet FortiMail Path Traversal Vulnerability (CVE-2026-104286)
Published Last modified In CISA KEV since Sources: Fortinet PSIRT, pwn.watch, CVE.org, SingCERT, BSI
- Actively exploited
- Source: VulnCheck KEV (opens in a new tab), CSA/SingCERT How we classify
- Public exploit
What is affected, what to do
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, FortiMail 7.0 all versions may allow an unauthenticated attacker to write arbitrary files on the underlying system via crafted HTTP or HTTPS requests.
The vulnerability is being actively exploited; treat it as a priority. Update fortimail to version 7.6.7, FortiMail to version 7.4.9. Immediate actions, mitigation and detection rules are in the runbook below.
- Affected
- Fortinet FortiMail
lte 8.0.0..8.0.1 - Fortinet FortiMail
lte 7.6.0..7.6.6 - Fortinet FortiMail
lte 7.4.0..7.4.8 - Fortinet FortiMail
lte 7.2.0..7.2.9 - Fortinet FortiMail
lte 7.0.0..7.0.9
- Fortinet FortiMail
Not sure whether and how you are affected? Ask a question about this vulnerability
Metrics
9.8
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: Vendor (CNA), CVSS v3
9.8
CVSS v3
Severity Critical on the scale from 0 to 10.
Source: Fortinet PSIRT, pwn.watch, CVE.org, SingCERT, BSI
4.6 %
EPSS score
Moderate — model estimates 1-10% exploitation likelihood.
Source: FIRST EPSS, percentile 91.6
Show all metrics
- Severity
- Critical
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 246.11 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- actively exploitedSource: VulnCheck KEV (opens in a new tab), CSA/SingCERT How we classify
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 9.8 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 9.8
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 4.6 %
- Moderate — model estimates 1-10% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 91.6
- Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- Actively exploited
- Published
In CISA KEV since
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- CISA assessment (SSVC)
- Exploitation: active · automatable · Technical impact: total
- Source: CISA Vulnrichment, as of 2 October 2026
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-22
Response and mitigation
Why act now?
Prioritisation rationale
This flaw is network-reachable without authentication or user interaction. Arbitrary file write on a perimeter appliance typically escalates to code execution, persistence, and full visibility into an organisation's email traffic. Fortinet edge devices are a favoured initial-access target, and organisations exposing the FortiMail admin GUI or webmail to the internet are the primary victims. CISA does not flag known ransomware use, but exploitation likelihood is rated well above average and a public proof-of-concept should be assumed. Treat internet-exposed FortiMail as critical: patch or isolate within 24 hours. Internal-only instances with tight trusted-host restrictions can follow in the regular emergency patch cycle.
Runbook step 1
Immediate response (0-24 h)
- Inventory: Enumerate every FortiMail instance (hardware, VM, cloud) and check the firmware version. Affected releases are 7.2.0–7.2.9, 7.4.0–7.4.8, 7.6.0–7.6.6 and 8.0.0–8.0.1. Prioritise units whose web interface (admin GUI or webmail on TCP 443/80) is reachable from the internet.
- Patch: An official fix is available. Look up the fixed release for each branch in the Fortinet PSIRT advisory, and do not upgrade to any build inside the affected ranges. Schedule internet-facing systems for today.
- Cut exposure now: If patching must wait, remove HTTP/HTTPS from internet-facing interfaces (
config system interface→edit <port>→set allowaccesswithouthttp/https). Restrict administration to a dedicated management network. Mail flow (TCP 25/465/587) is not the described attack vector and can stay up. - Compromise check before patching: Back up the configuration and diff it against the last known-good copy. Look for new admin accounts, altered trusted hosts, and unfamiliar files or scripts. Patching does not remove files an attacker has already written.
- Rotate secrets: On any suspicion of compromise, rotate admin passwords, API tokens, LDAP/RADIUS bind accounts, and TLS keys and certificates stored on the appliance. Consider a factory reset with a clean install of the fixed firmware, following vendor guidance.
- Reporting obligations: For a confirmed compromise of a mail gateway in NIS2/KRITIS scope, start the 24-hour early-warning process towards the national CSIRT/BSI.
Runbook step 2
Mitigation layers
- Network segmentation: Expose the admin GUI only via a management VLAN or jump host. Drop inbound TCP 443/80 from the internet to the FortiMail management IP at the perimeter firewall. On FortiMail, additionally pin each admin account to fixed source networks with
set trusthost1..n. - Webmail behind reverse proxy/WAF: If webmail must stay external, publish it only through a reverse proxy or WAF. Reject requests whose URI or body contains:
- traversal sequences (
../,..%2f,%2e%2e,..%5c, double-encoded%252e) - NULL bytes (
%00,%2500,\x00)
- traversal sequences (
- IPS: On an upstream FortiGate or Suricata sensor, enable the current IPS signature for this Fortinet advisory in block mode. As a stopgap, use a generic Suricata rule on
http.uriwithcontent:"%00"pluspcre:"/\.\.(\/|%2f|%5c)/i", scoped to the FortiMail IP. - Egress control: Limit FortiMail outbound traffic to required destinations: DNS, NTP, FortiGuard update servers, upstream MTAs and LDAP. This frustrates reverse shells and tool staging after a successful file write.
- IAM/least privilege: Minimise admin profiles, enforce MFA on GUI logins and disable unused accounts. The bug is pre-auth, but hardening limits follow-on activity.
- Logging: Forward event, history and admin logs via syslog over TLS to the SIEM. Local logs on a compromised appliance cannot be trusted.
- Network segmentation: Expose the admin GUI only via a management VLAN or jump host. Drop inbound TCP 443/80 from the internet to the FortiMail management IP at the perimeter firewall. On FortiMail, additionally pin each admin account to fixed source networks with
Runbook step 3
Detection rules
-
Web/proxy logs: Hunt for requests to FortiMail containing traversal or NULL-byte patterns, especially upload-style POST/PUT requests. Example SPL:
index=proxy dest=<fortimail_ip> (uri="*..%2f*" OR uri="*%2e%2e*" OR uri="*../*" OR uri="*%00*" OR uri="*%2500*") | stats count by src_ip, uri, status -
Zeek/Suricata telemetry: Match
http.logentries to the FortiMail IP whereurihits/(\.\.|%2e%2e)(\/|%2f|%5c)|%00/i. Inconn.log, look for FortiMail initiating outbound sessions to unapproved destinations, such as high ports or VPS/hosting ranges. -
FortiMail event/admin logs (syslog): Alert on:
- new or modified admin accounts
trusthostchanges- configuration changes outside maintenance windows
- unscheduled reboots or firmware events
Sigma shape:
logsource: product: fortimail/selection: subtype: admin, msg|contains: ['added','changed']/filter: src_ip in mgmt_net. -
Integrity drift: Pull the running configuration on a schedule and compare it against a hashed baseline. Treat any unticketed drift as an incident. Unexpected files in web-served paths indicate a webshell.
-
Mail-flow anomalies: Newly appearing forwarding or archiving rules, changed relay hosts, or BCC policies can indicate persistence or mail interception after compromise.
-
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
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, FortiMail 7.0 all versions may allow an unauthenticated attacker to write arbitrary files on the underlying system via crafted HTTP or HTTPS requests.
Source: fortinet_rss, pwn.watch, NVD (NIST), cvelistv5, CSA/SingCERT, BSI WID Portal, BSI CSAF, CISA KEV Catalog
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| Fortinet | FortiMail |
|
|
| fortinet | fortimail |
|
|
Vendors and products
Weakness classes (CWE)
CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Base
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
Entry at MITRE CWE-22
Public exploit references
Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.
| CISA KEV Catalog | CISA Known Exploited Vulnerability (opens in a new tab)cisa.gov | actively exploited | |
| CSA/SingCERT | Active Exploitation of Vulnerability in Fortinet FortMail (opens in a new tab)CSA/SingCERT | actively exploited | |
| PoC-in-GitHub (nomi-sec) | CVE-2026-104286-PoC (opens in a new tab)github.com | PoC (publicly reported)reported, not verified | |
| PoC-in-GitHub (nomi-sec) | fortimail-cve-2026-104286-response (opens in a new tab)github.com | PoC (publicly reported)reported, not verified | |
| PoC-in-GitHub (nomi-sec) | fortimail-zero-day-cve-2026-104286 (opens in a new tab)github.com | PoC (publicly reported)reported, not verified |
References & sources
- fortiguard.fortinet.compsirt/FG-IR-26-175Mitigation, Vendor advisory
- cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2026-1042…government-resource, US government resource
- pwn.watchpwn.watch: FortiMail unauthenticated file-write zero-day CVE-2026-104286pwn-watch
- fortiguard.comFortinet PSIRT FG-IR-26-175pwn-watch
- CSA/SingCERTCSA Singapore alertpwn-watch
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
NVD analysis modifiedNVD
Record modifiedfortinet.com
Description added or changed
Show 2 original changes
Individual changes of this event as published by NVD Type Action Before After Description changed An improper limitation of a pathname to a restricted directory ('path traversal') vulnerability in Fortinet FortiMail 8.0.0, FortiMail 7.6.0 through 7.6.5, FortiMail 7.4.0 through 7.4.7, FortiMail 7.2.0 through 7.2.9, FortiMail 7.0 all versions may allow an unauthenticated attacker to write arbitrary files on the underlying system via crafted HTTP or HTTPS requests.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, FortiMail 7.0 all versions may allow an unauthenticated attacker to write arbitrary files on the underlying system via crafted HTTP or HTTPS requests.Affected versions (publisher) added —Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/104xxx/CVE-2026-104286.json">CVE-2026-104286</a>Source identifier: psirt@fortinet.com
NVD analysis modifiedNVD
Product mapping changed:- Fortinet FortiMail (7.6.0 – before 7.6.7; 8.0.0 – before 8.0.2; 7.0.0 – through 7.0.9; 7.2.0 – through 7.2.9; 7.4.0 – before 7.4.9)
Show the original change
Individual changes of this event as published by NVD Type Action Before After Product configuration changed OR *cpe:2.3:a:fortinet:fortimail:*:*:*:*:*:*:*:* versions from (including) 7.2.0 up to (including) 7.4.8 *cpe:2.3:a:fortinet:fortimail:*:*:*:*:*:*:*:* versions from (including) 7.6.0 up to (including) 7.6.6 *cpe:2.3:a:fortinet:fortimail:*:*:*:*:*:*:*:* versions from (including) 8.0.0 up to (including) 8.0.1OR *cpe:2.3:a:fortinet:fortimail:*:*:*:*:*:*:*:* versions from (including) 7.6.0 up to (excluding) 7.6.7 *cpe:2.3:a:fortinet:fortimail:*:*:*:*:*:*:*:* versions from (including) 8.0.0 up to (excluding) 8.0.2 *cpe:2.3:a:fortinet:fortimail:*:*:*:*:*:*:*:* versions from (including) 7.0.0 up to (including) 7.0.9 *cpe:2.3:a:fortinet:fortimail:*:*:*:*:*:*:*:* versions from (including) 7.2.0 up to (including) 7.2.9 *cpe:2.3:a:fortinet:fortimail:*:*:*:*:*:*:*:* versions from (including) 7.4.0 up to (excluding) 7.4.9Source identifier: nvd@nist.gov
Record modifiedfortinet.com
Description added or changed
Show 2 original changes
Individual changes of this event as published by NVD Type Action Before After Description changed 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.An improper limitation of a pathname to a restricted directory ('path traversal') vulnerability in Fortinet FortiMail 8.0.0, FortiMail 7.6.0 through 7.6.5, FortiMail 7.4.0 through 7.4.7, FortiMail 7.2.0 through 7.2.9, FortiMail 7.0 all versions may allow an unauthenticated attacker to write arbitrary files on the underlying system via crafted HTTP or HTTPS requests.Affected versions (publisher) added —Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/104xxx/CVE-2026-104286.json">CVE-2026-104286</a>Source identifier: psirt@fortinet.com
Record modifiedCISA ADP
CISA assessment (SSVC): exploitation: active, automatable: yes
Show 2 original changes
Individual changes of this event as published by NVD Type Action Before After SSVC assessment removed {"id":"CVE-2026-104286","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-01T00:00:00+00:00"}—SSVC assessment added —{"id":"CVE-2026-104286","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-02T03:55:37.976071Z"}Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0
Show 6 older changes
Initial analysis by NVDNVD
Newly listed as affected:- Fortinet FortiMail (7.2.0 – through 7.4.8; 7.6.0 – through 7.6.6; 8.0.0 – through 8.0.1)
Show 3 original changes
Individual changes of this event as published by NVD Type Action Before After Product configuration added —OR *cpe:2.3:a:fortinet:fortimail:*:*:*:*:*:*:*:* versions from (including) 7.2.0 up to (including) 7.4.8 *cpe:2.3:a:fortinet:fortimail:*:*:*:*:*:*:*:* versions from (including) 7.6.0 up to (including) 7.6.6 *cpe:2.3:a:fortinet:fortimail:*:*:*:*:*:*:*:* versions from (including) 8.0.0 up to (including) 8.0.1Reference type added —Fortinet, Inc.: https://fortiguard.fortinet.com/psirt/FG-IR-26-175 Types: Mitigation, Vendor AdvisoryReference type added —CISA-ADP: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-104286 Types: US Government ResourceSource identifier: nvd@nist.gov
Record modifiedCISA ADP
CISA assessment (SSVC): exploitation: active, automatable: yes
Show 2 original changes
Individual changes of this event as published by NVD Type Action Before After SSVC assessment removed {"id":"CVE-2026-104286","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-01T20:02:06.190902Z"}—SSVC assessment added —{"id":"CVE-2026-104286","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-01T00:00:00+00:00"}Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0
CISA KEV entry updated9119a7d8…
4 individual changes: Date Added, Due Date, Required Action, Vulnerability Name
Show 4 original changes
Individual changes of this event as published by NVD Type Action Before After Date Added added —2026-10-01Due Date added —2026-10-01Required Action added —2026-10-01Vulnerability Name added —2026-10-01Source identifier: 9119a7d8-5eab-497f-8521-727c672e3725
Record modifiedCISA ADP
CISA assessment (SSVC): exploitation: active, automatable: yes
Show 2 original changes
Individual changes of this event as published by NVD Type Action Before After SSVC assessment removed {"id":"CVE-2026-104286","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-01T19:38:28.720380Z"}—SSVC assessment added —{"id":"CVE-2026-104286","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-01T20:02:06.190902Z"}Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0
Receivedfortinet.com
CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness type: CWE-22
Description added or changed
New references:Show 5 original changes
Individual changes of this event as published by NVD Type Action Before After Description added —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.CVSS added —AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HWeakness type (CWE) added —CWE-22Affected versions (publisher) added —New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/104xxx/CVE-2026-104286.json">CVE-2026-104286</a>Reference added —https://fortiguard.fortinet.com/psirt/FG-IR-26-175Source identifier: psirt@fortinet.com
Record modifiedCISA ADP
CISA assessment (SSVC): exploitation: none known, automatable: yes
Show 2 original changes
Individual changes of this event as published by NVD Type Action Before After Reference added —https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-104286SSVC assessment added —{"id":"CVE-2026-104286","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-01T19:38:28.720380Z"}Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0
Linked advisories
- Exploited Fortinet FortiMail Zero-Day Calls for Urgent ActionSecurityWeek
- NCSC-2026-0398 [1.00] [M/H] Kwetsbaarheid verholpen in Fortinet FortiMailNCSC-NL
- Critical FortiMail Zero-Day Flaw Exploited in Attacks Allows Unauthenticated Arbitrary File WritesThe Hacker News
- Vulnérabilité dans Fortinet FortiMail (02 octobre 2026)CERT-FR (ANSSI)
- Fortinet warns of critical FortiMail flaw exploited in zero-day attacksBleepingComputer
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<a href="https://intel.neosec.eu/en/cve/CVE-2026-104286"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-104286.svg?lang=en" alt="CVE-2026-104286 – NEOSEC Intel" height="20"></a>