Fortinet Patches Critical Vulnerabilities in FortiMonitorOnSight, Chrome Extension
Fortinet patched 10 vulnerabilities including two critical authentication flaws, CVE-2026-84390 (CVSS 9.6) and CVE-2026-84388 (CVSS 9.1), in FortiMonitorOnSight and the FortiPAM Chrome extension.
Fortinet's September patch release fixes CVE-2026-84390, a sensitive-information issue in the FortiMonitorOnSight web portal that lets unauthenticated attackers bypass authentication with forged or reused JWTs. CVE-2026-84388 is an improper authentication flaw in the Fortinet Privileged Access Agent Chrome extension that can allow attackers to proxy a user's browser traffic via a malicious website, requiring upgrades to both FortiPAM 1.9.1/1.8.4 and extension 8.0.1.123+. High-severity information disclosure in FortiSandbox (CVE-2026-26084) and man-in-the-middle risk in the FortiOS/FortiProxy Agentless ZTNA portal (CVE-2026-84393) were also fixed, alongside medium/low issues across FortiManager, FortiAnalyzer, FortiSOAR, FortiClient, FortiSIEM and others. Fortinet did not indicate any of the flaws are being exploited in the wild.
- CVE-2026-84390 (CVSS 9.6) enables JWT forgery to bypass FortiMonitorOnSight authentication
- CVE-2026-84388 (CVSS 9.1) lets attackers proxy browser traffic through the FortiPAM Chrome extension
- Fix requires coordinated upgrades of FortiPAM and extension 8.0.1.123+
- High-severity fixes also cover FortiSandbox info disclosure and ZTNA portal MitM
- No mention of in-the-wild exploitation
Vulnerabilities mentioned
All| CVE | Vulnerability | CVSS | EPSS | Signals | Published |
|---|---|---|---|---|---|
| CVE-2026-26084 | Improper Access Control in Fortinet FortiSandbox Exposes Sensitive Data | 9.9 | <1% | ||
| CVE-2026-84388 | Unauthenticated UI-Layer Flaw in Fortinet FortiPAM Chrome Extension | 9.6 | <1% | PoC | |
| CVE-2026-84390 | Sensitive Information in Source Code in Fortinet FortiMonitorOnSight (CVSS 9.8) | 9.8 | — | ||
| CVE-2026-84393 | Certificate Host-Mismatch Validation Flaw in FortiOS and FortiProxy ZTNA | 8.1 | <1% |
From the original article
1 min read at securityweek.com
The critical, unauthenticated bugs allow attackers to bypass authentication and proxy a user’s browser traffic. The post Fortinet Patches Critical Vulnerabilities in FortiMonitorOnSight, Chrome Extension appeared first on SecurityWeek.
By Ionut Arghire · securityweek.com
A short excerpt; the article and its images belong to the publisher. Summary, key facts and assessment above are AI-written from the article and can be wrong.