If your FortiGate runs an affected FortiOS release, upgrade to a fixed release that is still supported for your exact model and upgrade path. If you cannot patch immediately, disable SSL-VPN temporarily. Disabling SSL-VPN web mode alone is not an adequate workaround.
What is CVE-2024-21762?
CVE-2024-21762 is a critical out-of-bounds write vulnerability in FortiOS SSL-VPN, tracked by Fortinet as advisory FG-IR-24-015. A remote, unauthenticated attacker can send crafted HTTP requests to the SSL-VPN service. The resulting memory corruption and flow redirection may allow arbitrary code or command execution on the device. Tenable identifies the vulnerable component as the sslvpnd daemon. CERT-EU Security Advisory 2024-018; Tenable analysis.
The reported severity score varies by source: CERT-EU gives CVSS 9.8, while Tenable’s table reports CVSSv3 9.6. Those are source-specific scores; the cited material does not explain the difference. CERT-EU; Tenable.
Which FortiOS versions are affected?
CERT-EU lists the following FortiOS ranges as affected by CVE-2024-21762:
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- Compact and Efficient Design: The FortiGate 40F is designed for small to mid-sized businesses and enterprise branch offices, featuring a compact, fanless desktop form factor that ensures quiet operation and minimizes space usage.
- Robust Connectivity Options: Equipped with 5 GE RJ45 ports, including 1 WAN port and 4 internal ports, this model provides essential connectivity and flexibility for various network configurations in a small-scale environment.
- High-Performance Security: Offers up to 1 Gbps IPS throughput and 600 Mbps threat protection throughput, using Fortinet’s purpose-built security processor technology to deliver industry-leading performance and protection for SSL encrypted traffic.
- Advanced Threat Protection: Integrated with Fortinet’s AI-powered FortiGuard Labs, the FortiGate 40F offers comprehensive cybersecurity, identifying and mitigating both known and unknown threats to maintain robust security across your network.
- Simplified Management and Deployment: Features a user-friendly management console that provides comprehensive network automation and visibility, coupled with Zero Touch Integration with Fortinet’s Security Fabric for easy deployment.
| FortiOS branch | Affected versions | Minimum fixed version listed in February 2024 |
|---|---|---|
| 7.4 | 7.4.0–7.4.2 | 7.4.3 |
| 7.2 | 7.2.0–7.2.6 | 7.2.7 |
| 7.0 | 7.0.0–7.0.13 | 7.0.14 |
| 6.4 | 6.4.0–6.4.14 | 6.4.15 |
| 6.2 | 6.2.0–6.2.15 | 6.2.16 |
| 6.0 | All versions | 6.0.18 |
The affected ranges are from CERT-EU; the historical minimum fixed builds are from Tenable’s February 2024 version table. FortiOS 7.6 was listed by Tenable as not affected. These fixed-build numbers identify the original fixes, not a recommendation to install an old release in 2026.
What should you upgrade to?
Choose a release that includes the fix and is currently supported for your FortiGate model and branch. The minimum fixed version in the table is a useful historical reference, but it may no longer be supported or be a valid direct upgrade target. Check Fortinet’s current product release notes and upgrade guidance for the device’s exact model, current firmware, and permitted upgrade path before scheduling the change.
Rank #2
- INTEGRATED FIREWALL APPLIANCE AND SECURITY SERVICES: Comes with FortiGate-40F Firewall Appliance, 1 year of FortiCare Premium, and FortiGuard Unified Threat Protection.
- UTP SECURITY FEATURES: Offers protection from advanced threats with DNS filtering, URL filtering, video filtering, and controls against botnets.
- IDEAL FOR SMALLER SETTINGS: Best suited for small to mid-sized businesses needing reliable security without the complexity of larger systems.
- CONTINUOUS SUPPORT AND MAINTENANCE: FortiCare Premium ensures that technical help is readily available to manage and troubleshoot issues.
- COMPACT AND EFFECTIVE: Provides a powerful, yet compact security solution that effectively protects against a wide range of cyber threats.
- Identify the FortiGate model and installed FortiOS version.
- Compare the installed version with the affected range for its branch.
- Use Fortinet’s current release notes and upgrade guidance to select a supported fixed target and confirm the required intermediate upgrades, if any.
- Plan and perform the upgrade according to your organization’s change process, then verify the device is running the intended firmware.
If your installation is FortiProxy rather than FortiGate, do not apply the FortiOS table to it. Ireland’s NCSC lists affected FortiProxy releases as 7.4.0–7.4.2, 7.2.0–7.2.8, 7.0.0–7.0.14, 2.0.0–2.0.13, and all versions of 1.0, 1.1, and 1.2. Tenable’s February 2024 table lists minimum fixed FortiProxy releases 7.4.3, 7.2.9, 7.0.15, and 2.0.14, with migration from the affected 1.2 branch. Confirm the appropriate current path with product-specific Fortinet guidance. Ireland’s NCSC advisory; Tenable.
What if you cannot patch immediately?
Temporarily disable SSL-VPN until you can install a fixed release. Ireland’s NCSC reports that disabling web mode alone is not a valid workaround; it does not disable the vulnerable SSL-VPN service. Follow the product’s current administration guidance for the exact way to disable SSL-VPN in your configuration. Ireland’s NCSC advisory.
The Tool Desk
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- Extensive Connectivity Options: The FortiGate 60F is designed with 10 GE RJ45 ports, including 2 WAN ports, 1 DMZ port, and 7 internal ports, offering broad flexibility and high-density connections for diverse enterprise networking needs.
- Superior Performance for Secure Networks: Features powerful system-on-a-chip acceleration to deliver top-tier security with 1.4 Gbps IPS throughput and 700 Mbps threat protection throughput, ensuring effective defense against advanced threats.
- Enhanced SSL Inspection and SD-WAN Capabilities: Utilizes purpose-built security processor technology to provide the industry's highest SSL inspection performance and robust SD-WAN functionality for secure, high-speed network operations.
- Simple and Effective Management: Comes equipped with a user-friendly management console that supports comprehensive network automation and visibility, alongside Zero Touch Integration with Fortinet's Security Fabric for streamlined deployment.
- Advanced Security Features: Leverages continuous threat intelligence from AI-powered FortiGuard Labs, identifying and mitigating both known and unknown threats, enhancing security across all network traffic, whether encrypted or not.
What is known about exploitation?
Ireland’s NCSC advisory records that on March 20, 2024, its CSIRT added information about a public proof of concept and active exploitation. It also notes that exploitation activity increased after release of a detailed public PoC and that CVE-2024-21762 was included in CISA’s Known Exploited Vulnerabilities catalog. These are historical observations from 2024, not evidence of the level of exploitation on October 4, 2026. The cited material does not establish a current exploitation statistic. Ireland’s NCSC advisory.
CERT-EU’s Security Advisory 2024-018, released February 9, 2024, said: “It is recommended updating as soon as possible.” CERT-EU.
Quick Recap
Best Value
- Robust Port Configuration: The FortiGate 120G is equipped with 18 GE RJ45 ports, including 1 management port and 1 HA port, alongside 16 switch ports. It also features 8 GE SFP slots and 4 10GE SFP+ slots, providing versatile connectivity options for complex network setups.
- Cutting-edge Performance with SP5 Acceleration: Powered by SP5 hardware acceleration, the device ensures unmatched performance, making it ideal for enterprises requiring rapid application identification, efficient business operations, and robust security.
- Dual AC Power Supplies: Designed with dual non-hot swappable AC power supplies, the FortiGate 120G ensures uninterrupted service and operational reliability, critical for maintaining mission-critical network activities.
- Superior Security Features: Integrated with Fortinet’s Security Fabric, the FortiGate 120G offers advanced threat protection, real-time SSL inspection, and AI-powered FortiGuard services, providing comprehensive defense against modern cyber threats.
- Streamlined Network Management: Features such as the FortiLink protocol allow seamless integration of security and network management, enabling centralized control and simplified operations across all networked FortiGate devices.
Rank #4
- HARDWARE PLUS SECURITY SERVICES: FortiGate-60F Firewall Appliance bundled with 1 year of FortiCare Premium and FortiGuard Unified Threat Protection.
- UNIFIED THREAT PROTECTION (UTP): Secures against advanced online threats with comprehensive web filtering and anti-botnet technologies.
- OPTIMIZED FOR MEDIUM-SIZED BUSINESSES: Tailored for businesses needing robust security without the infrastructure of larger enterprises.
- RELIABLE CUSTOMER SUPPORT: FortiCare Premium ensures high-quality support and service continuity.
- EFFECTIVE PROTECTION: Employs advanced filtering technologies to safeguard against sophisticated threats.
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