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Fortinet FortiSandbox Vulnerability Allows Unauthenticated Attackers to Access Sensitive Information
Fortinet fixed CVE-2026-26084, an unauthenticated access-control flaw in FortiSandbox GUI rated 8.9 CVSS, with no known exploitation yet.
Fortinet disclosed CVE-2026-26084 (advisory FG-IR-26-166), a CWE-284 improper access control flaw in the GUI of FortiSandbox, FortiSandbox Cloud and FortiSandbox PaaS, rated 8.9 CVSS v3.1. An unauthenticated remote attacker can send specially crafted HTTP requests to control NAT rules and expose sensitive information. Affected versions include FortiSandbox 4.4.0-4.4.8 and 5.0.0-5.0.5 (plus Cloud/PaaS 5.0.4-5.0.5), fixed in 4.4.9 and 5.0.6. Fortinet researcher Adham El Karn found the flaw internally and the September 8 advisory reports no known exploitation.
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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.
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CISA Flags Exploited Cisco, Citrix, Fortinet Flaws, Sets Sept. 12 Federal Patch Deadline
CISA adds actively exploited Cisco, Citrix, and Fortinet edge-device flaws to KEV catalog, ordering federal agencies to patch by September 12, 2026.
CISA added CVE-2026-20079 (Cisco Secure Firewall Management Center authentication bypass, CVSS 10.0), CVE-2026-19490 (Citrix NetScaler ADC/Gateway authentication bypass, CVSS 9.3), and CVE-2025-25249 (FortiOS heap buffer overflow, CVSS 7.3) to the Known Exploited Vulnerabilities catalog with a September 12, 2026 deadline for FCEB agencies. Cisco confirmed active exploitation of CVE-2026-20079 in August 2026, while Previdian honeypots logged 56 NetScaler exploitation attempts since September 3. SOCRadar attributes Fortinet exploitation to a financially motivated Russian-speaking actor deploying the PivotC2 Node.js RAT, infecting 178 of over 3,000 targeted IP addresses, mostly in the US.
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Fortinet Code Execution Flaw Exploited in PivotC2 RAT Attacks
Threat actors exploit Fortinet heap-based buffer overflow CVE-2025-25249 to deploy PivotC2 RAT, infecting 178 devices and exfiltrating data from US targets.
SOCRadar reports exploitation of an unauthenticated remote code execution vulnerability, CVE-2025-25249 (CVSS 7.4), patched in January in FortiOS and FortiSwitchManager. Attackers scanned over 30,000 IP addresses, infected 178 devices with PivotC2 RAT, and at least two intrusions resulted in data exfiltration, primarily targeting US entities. SOCRadar attributes attacks to a likely Russian-speaking cybercrime actor and suggests the RAT was AI-assisted, in use since July 2026. CISA added the CVE to the KEV catalog with a three-day BOD 26-04 patch deadline for federal agencies.
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Thai Broadband Provider Hacked via Fortinet Vulnerability
Hackers exploited Fortinet CVE-2024-21762 RCE to breach Thai broadband provider 3BB, deploying MeshCentral backdoors and credential-harvesting tools across its network.
Hunt.io uncovered an intrusion staging directory in Thailand containing 298 files of custom tooling built for Triple T Broadband (3BB) and its former owner Jasmine. Initial access came via fingerprinting a FortiGate SSL-VPN appliance and exploiting CVE-2024-21762 for remote code execution, after probing CVE-2018-13379, CVE-2022-42475, and CVE-2023-27997. The actor also probed F5 BIG-IP for CVE-2021-22986, CVE-2022-1388, and CVE-2023-46747, escalated privileges with PwnKit and Dirty COW, used MeshCentral as a C2 backdoor, harvested SSH/database/SNMP/Radius credentials, deployed PHP web shells, and ran cleanup scripts to hide the intrusion.
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Gunra Ransomware Exploits Fortinet FortiOS, FortiProxy Flaws to Breach Networks
CISA, FBI, and South Korean agencies warn Gunra ransomware, with 51 victims since April 2025, exploits Fortinet flaws for double-extortion attacks on critical infrastructure.
CISA, the FBI, and South Korean agencies warned of Gunra ransomware attacks targeting healthcare, financial services, government, and professional services worldwide. The Conti-derived operation exploits internet-facing Fortinet FortiOS and FortiProxy flaws CVE-2024-55591 and CVE-2025-24472 for initial access, then deploys double extortion with Salsa20/ChaCha20 encryption and publishes non-payers on a leak site within five to seven days. Ransomware.Live lists 51 victims since April 2025, mostly in South Korea, Brazil, Spain, Thailand, and Hong Kong. The group uses Impacket tools for SMB lateral movement and NTDS credential dumping, tampers with VDI authentication to accept a designated OTP value to bypass MFA, and launched a RaaS affiliate program in January 2026 under the new alias Golden Community.
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FortiSandbox Vulnerability Allows Attackers to Access Sensitive Information via Crafted HTTP Requests
Fortinet disclosed CVE-2026-26084 (CVSS 8.9), an unauthenticated information-disclosure flaw in the FortiSandbox web UI, urging upgrades.
Fortinet patched CVE-2026-26084, a CWE-284 improper access control flaw in the shared web UI of FortiSandbox, FortiSandbox Cloud, and FortiSandbox PaaS that lets unauthenticated attackers read sensitive data via crafted HTTP requests. Affected releases include FortiSandbox 5.0.0-5.0.5 and 4.4.0-4.4.8, Cloud 5.0.4-5.0.5, and PaaS 5.0.4-5.0.5; fixes arrive in 5.0.6+ and 4.4.9+, while FortiSandbox 5.2 and Cloud 4.4 are unaffected. The issue was found internally by Fortinet's Product Security team, and the company reports no evidence of exploitation in the wild. Disclosure carries only confidentiality impact, but exposed sandbox configurations and logs could aid follow-on attacks.
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Fortinet Vulnerability Ransomware
Ransomware operators are exploiting a Fortinet vulnerability, per the Infosecurity Magazine headline; article details unavailable.
Infosecurity Magazine's headline indicates ransomware activity tied to a Fortinet vulnerability. The article body was not available, so the specific CVE, affected versions and victim details are unconfirmed.
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Gunra Ransomware Exploits Fortinet Flaws to Target Critical Infrastructure
US and Korean agencies warn Gunra ransomware actors exploit Fortinet flaws and stealthily exfiltrate large data volumes, targeting critical infrastructure.
US and Korean authorities warned that Gunra ransomware actors exploit Fortinet vulnerabilities to gain access and use stealthy techniques to exfiltrate vast volumes of data, including from Microsoft services. The group is targeting critical infrastructure organizations. Defenders should prioritize Fortinet patching and watch for large, quiet data egress.
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FortiOS and FortiProxy ZTNA Validation Vulnerability Allows Attacker to Perform a Man-in-the-Middle Attack
Fortinet discloses high-severity certificate validation flaw CVE-2026-84393 in FortiOS and FortiProxy Agentless ZTNA portals enabling unauthenticated man-in-the-middle attacks.
Fortinet disclosed CVE-2026-84393 (CVSSv3 7.3, CWE-295) on September 8, 2026 under advisory FG-IR-26-174: improper certificate validation in the Agentless ZTNA portal of FortiOS and FortiProxy. An unauthenticated attacker on the network path could present a forged or mismatched certificate and intercept or tamper with traffic between the portal and backend destinations, with impact classified as information disclosure. Affected versions are FortiOS 7.6.1 through 7.6.6 and FortiProxy 7.6.2 through 7.6.6; the 8.0, 7.4 and 7.2 branches of both products are unaffected. Fortinet urges upgrading to 7.6.7 or later and reports no evidence of exploitation in the wild.
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CISA Adds 6 Known Exploited Flaws in Fortinet, Microsoft, and Adobe Software
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