Threat Intelligence / CVE / CVE-2026-35616

CVE-2026-35616 — Fortinet Forticlientems

CISA KEV

CVSS v3.1 9.8 (CRITICAL) · EPSS 25.2% (higher than 96.1% of all scored CVEs) · Priority 9/10 · Published 2026-04-04

As of 2026-04-06, CVE-2026-35616 is a CRITICAL-severity vulnerability in Fortinet Forticlientems, CVSS v3.1 9.8, EPSS 25.2% (96.1th percentile). It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-04-06), with a US federal remediation deadline of 2026-04-09. Threadlinqs Intelligence links 5 tracked threat campaigns to CVE-2026-35616, most recently “FortiBleed Credential Theft Campaign Linked to INC and Lynx Ransomware Operations”.

Last updated: 2026-04-06

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 161 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): 25.2% probability of exploitation in the next 30 days, higher than 96.1% 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 2026-04-06

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. It currently carries a trending score of 44 in the Threadlinqs vulnerability feed.

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

5 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.

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) — HIGH · 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

Seeded from threat-derived and not yet processed by the Threadlinqs enrichment pipeline, so blank CVSS, EPSS or KEV fields above mean NOT MEASURED rather than measured-absent.

Full detection coverage & IOCs for threats exploiting CVE-2026-35616 are available via the Threadlinqs MCP server (Purple tier). View plans →

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