CVE-2026-35616 — Fortinet Forticlientems

What is CVE-2026-35616?

Critical improper access control vulnerability (CWE-284) in Fortinet FortiClient Endpoint Management Server (EMS) versions 7.4.5 and 7.4.6. The flaw resides in the API authentication and authorization layer, enabling unauthenticated remote attackers to completely bypass access controls and execute arbitrary code or commands via specially crafted API requests to the management interface (ports 443 HTTPS and 8013 telemetry). Requires no authentication, no user interaction, and has low attack complexity. Active zero-day exploitation was first recorded by watchTowr on March 31, 2026 — four days before Fortinet published the advisory. Defused Cyber independently confirmed exploitation via their Radar system. CISA added this CVE to the KEV catalog on April 6, 2026 with an unusually tight three-day remediation deadline of April 9, 2026. Shadowserver identified approximately 2,000 exposed FortiClient EMS instances online, concentrated in the United States and Germany. This is the second critical FortiClientEMS vulnerability exploited in rapid succession after CVE-2026-21643. Fortinet released emergency hotfixes 7.4.5.2111 and 7.4.6.2170 with a permanent fix expected in FortiClient EMS 7.4.7. The 7.2.x branch is not affected.

The record classifies CVE-2026-35616 under weakness class CWE-284. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 2 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 207 days ago.

Severity and exploitation probability

CVSS v3.1 base score: 9.8 — CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (FIRST): 9.0% probability of exploitation in the next 30 days, higher than 95.1% of all scored CVEs
CISA KEV: Listed since 2026-04-06, federal remediation deadline 2026-04-09
Threadlinqs priority: 9/10 — CISA KEV-listed, which Threadlinqs floors at 9
Published: 2026-04-04, last modified 2026-07-08

Is CVE-2026-35616 being exploited?

CISA added CVE-2026-35616 to the Known Exploited Vulnerabilities catalog on 2026-04-06, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2026-04-09 under BOD 22-01. Weaponised exploit code for CVE-2026-35616 is publicly available. 8 public proof-of-concept repositories are tracked for this identifier. A ProjectDiscovery Nuclei detection template exists (http/cves/2026/CVE-2026-35616.yaml). It currently carries a trending score of 59 in the Threadlinqs vulnerability feed.

Alaatk/CVE-2026-35616 (github)
BishopFox/CVE-2026-35616-check (github)
0xBlackash/CVE-2026-35616 (github)
keraattin/CVE-2026-35616 (github)
wa6n3r/CVE-2026-35616 (github)
fevar54/CVE-2026-35616-detector.py (github)
fevar54/forticlient_ems_cve_2026_35616_poc.py (github)
HORKimhab/CVE-2026-35616 (github)

Affected products and versions

Fortinet: Forticlientems 7.4.5, Forticlientems 7.4.6

How to fix CVE-2026-35616

The record marks a vendor fix as available for CVE-2026-35616. Patch reference: https://fortiguard.fortinet.com/psirt/FG-IR-26-099. Vendor advisory: https://fortiguard.fortinet.com/psirt/FG-IR-26-099. Because CVE-2026-35616 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2026-04-09. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

Threat activity tracking CVE-2026-35616

7 tracked threats in the Threadlinqs corpus reference CVE-2026-35616, either in the campaign’s CVE list or as an indicator on the campaign record.

INC Ransomware Operators Use Claude AI and Phantom Framework; Exposed Data Shows 8,257 Messages and 46 Victim-Specific Encryptor Builds (CVE-2026-35616, CVE-2024-57727, CVE-2026-41940) — CRITICAL · 2026-10-21
INC and The Gentlemen Ransomware: Exposed AI-Executed, Human-Approved Attack Infrastructure (Phantom framework) — CRITICAL · 2026-10-20
FortiBleed Credential Theft Campaign Linked to INC and Lynx Ransomware Operations — CRITICAL · 2026-07-05
FortiBleed Credential-Harvesting Campaign Against 430,000 FortiGate Firewalls Feeds INC Ransom and Lynx Ransomware Operations — CRITICAL · 2026-07-02
EKZ Infostealer Campaign — FortiClient EMS CVE-2026-35616 Abused via on_connect Script Injection (Arctic Wolf, May 2026) — CRITICAL · 2026-05-27
FortiClient EMS Pre-Authentication API Bypass Leading to RCE (CVE-2026-35616) — Active Zero-Day Exploitation — CRITICAL · 2026-04-06
CVE-2026-35616: Fortinet FortiClientEMS Pre-Authentication API Bypass Leading to Remote Code Execution (CISA KEV) — CRITICAL · 2026-04-06

Sources

Enriched from CVE.org, FIRST EPSS, CISA KEV, public proof-of-concept repositories, ProjectDiscovery Nuclei. Last verified by Threadlinqs on 2026-10-10.