Threat Intelligence / CVE / CVE-2026-21643

CVE-2026-21643 — Fortinet FortiClient EMS

CISA KEV

CVSS v3.1 9.8 (CRITICAL) · EPSS 62.5% (higher than 98.3% of all scored CVEs) · Priority 9/10 · Published 2026-02-06

As of 2026-04-16, CVE-2026-21643 is a CRITICAL-severity vulnerability in Fortinet FortiClient EMS, CVSS v3.1 9.8, EPSS 62.5% (98.3th percentile). It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-04-13), with a US federal remediation deadline of 2026-04-16. Threadlinqs Intelligence links 2 tracked threat campaigns to CVE-2026-21643, most recently “CVE-2026-21643: Fortinet FortiClient EMS SQL Injection Enables Unauthenticated RCE — Actively Exploited in the Wild”.

Last updated: 2026-04-16

What is CVE-2026-21643?

Unauthenticated SQL injection vulnerability in Fortinet FortiClient EMS (CWE-89). FortiClient EMS operates as the central management plane for Fortinet endpoint security stack. The flaw allows a remote attacker to execute unauthorized code or commands via crafted HTTP requests without authentication. Actively exploited against internet-exposed EMS instances. CISA KEV added 2026-04-13 with accelerated remediation deadline 2026-04-16. Parallels the 2024 FortiClient EMS SQLi (CVE-2023-48788) exploitation pattern.

The record classifies CVE-2026-21643 under weakness class CWE-89. 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. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 219 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): 62.5% probability of exploitation in the next 30 days, higher than 98.3% of all scored CVEs
CISA KEV: Listed since 2026-04-13, federal remediation deadline 2026-04-16
Threadlinqs priority: 9/10 — CISA KEV-listed, which Threadlinqs floors at 9
Published: 2026-02-06, last modified 2026-04-16

Is CVE-2026-21643 being exploited?

CISA added CVE-2026-21643 to the Known Exploited Vulnerabilities catalog on 2026-04-13, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2026-04-16 under BOD 22-01. It currently carries a trending score of 50 in the Threadlinqs vulnerability feed.

Affected products and versions

(vendor unspecified): Fortinet FortiClient EMS

How to fix CVE-2026-21643

Vendor advisory: https://fortiguard.fortinet.com/psirt/FG-IR-25-1142. Because CVE-2026-21643 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2026-04-16. 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-2026-21643

2 tracked threats in the Threadlinqs corpus reference CVE-2026-21643, either in the campaign’s CVE list or as an indicator on the campaign record.

CVE-2026-21643: Fortinet FortiClient EMS SQL Injection Enables Unauthenticated RCE — Actively Exploited in the Wild — CRITICAL · 2026-04-16
CISA KEV Catalog Update: Seven Actively Exploited Vulnerabilities Added 2026-04-13 (Microsoft, Adobe, Fortinet) — CRITICAL · 2026-04-13

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-2026-21643 are available via the Threadlinqs MCP server (Purple tier). View plans →

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