CVE-2024-50565: Fortinet FortiWeb Auth Bypass Vulnerability

CVE-2024-50565 Overview

CVE-2024-50565 is an improper restriction of communication channel to intended endpoints vulnerability [CWE-923] affecting multiple Fortinet products. The flaw resides in the FortiGate to FortiManager (FGFM) authentication handshake between managed devices and their management server. An unauthenticated attacker positioned in a man-in-the-middle (MITM) location can intercept the FGFM authentication request and impersonate the management device, either FortiCloud or, under specific conditions, FortiManager. The vulnerability spans FortiOS, FortiProxy, FortiManager, FortiAnalyzer, FortiVoice, and FortiWeb across multiple supported branches.

Critical Impact

A network-positioned attacker can impersonate the FortiCloud or FortiManager management server, compromising the confidentiality and integrity of the management channel for affected Fortinet devices.

Affected Products

• Fortinet FortiOS 7.4.0–7.4.3, 7.2.0–7.2.7, 7.0.0–7.0.14, 6.4.0–6.4.15, 6.2.0–6.2.16
• Fortinet FortiProxy 7.4.0–7.4.2, 7.2.0–7.2.9, 7.0.0–7.0.15, 2.0.0–2.0.14
• Fortinet FortiManager, FortiAnalyzer, FortiVoice, and FortiWeb across multiple 6.x and 7.x branches

Discovery Timeline

• 2025-04-08 - CVE-2024-50565 published to the National Vulnerability Database (NVD)
• 2025-07-25 - Last updated in NVD database

Technical Details for CVE-2024-50565

Vulnerability Analysis

The vulnerability exists in the FGFM protocol, which Fortinet devices use to communicate with FortiManager and FortiCloud for centralized configuration and policy management. During the FGFM authentication phase, the managed device does not adequately restrict or validate the communication channel to its intended management endpoint. An attacker with network access between the managed device and its management server can intercept the authentication request and respond as if they were the legitimate FortiCloud server or FortiManager appliance.

The weakness aligns with [CWE-923] (Improper Restriction of Communication Channel to Intended Endpoints) and [CWE-300] (Channel Accessible by Non-Endpoint). Successful exploitation undermines the trust boundary between Fortinet appliances and their management plane.

Root Cause

The root cause is insufficient endpoint verification during the FGFM authentication exchange. The managed device fails to cryptographically bind the session to the legitimate management server identity, allowing an interposing party to substitute its own authentication response. This is characteristic of incomplete or improperly enforced server certificate or identity validation in a custom management protocol.

Attack Vector

Exploitation requires a man-in-the-middle position on the network path between a managed Fortinet device and its management server. The attacker passively waits for, or actively triggers, an FGFM authentication request. The attacker then intercepts the handshake and responds in place of the genuine FortiCloud or FortiManager endpoint. User interaction is required and attack complexity is high because the adversary must already control or influence traffic on the management path. Once impersonation succeeds, the attacker can manipulate management communications affecting confidentiality, integrity, and availability of the managed device.

No verified public proof-of-concept code is available. See the FortiGuard Security Advisory FG-IR-24-046 for vendor technical details.

Detection Methods for CVE-2024-50565

Indicators of Compromise

• Unexpected FGFM session establishment from IP addresses that are not the authorized FortiManager or FortiCloud endpoints
• TLS certificate anomalies or mismatched server identities observed on FGFM connections (typically TCP/541)
• Configuration changes on managed devices that do not correlate with administrator activity in FortiManager audit logs
• Repeated FGFM authentication retries or session resets from managed devices

Detection Strategies

• Monitor outbound FGFM traffic and alert on connections to destinations outside the approved FortiCloud and FortiManager IP allowlist
• Correlate FortiManager-side session logs with managed-device FGFM logs to identify orphaned or duplicate authentication attempts
• Inspect network flows on the management VLAN for ARP spoofing, rogue DHCP, or BGP/route hijack conditions that enable MITM positioning

Monitoring Recommendations

• Centralize FortiOS, FortiManager, and FortiAnalyzer logs in a SIEM and build alerts for FGFM authentication anomalies
• Track changes to device management configuration and policy pushes against an authoritative change-control record
• Enable continuous monitoring of certificate chains presented during FGFM handshakes and alert on unexpected issuers or fingerprints

How to Mitigate CVE-2024-50565

Immediate Actions Required

• Upgrade all affected Fortinet products to fixed versions as documented in FG-IR-24-046
• Inventory every device running FortiOS, FortiProxy, FortiManager, FortiAnalyzer, FortiVoice, or FortiWeb and confirm whether it falls in the affected version ranges
• Restrict FGFM management traffic to dedicated, segmented networks or VPN tunnels that prevent attacker interposition

Patch Information

Fortinet has released fixed builds across the affected product lines. Administrators should consult the vendor advisory FG-IR-24-046 to identify the specific fixed version for each product branch and apply updates following Fortinet's upgrade path guidance.

Workarounds

• Constrain FGFM connections to known management IP addresses using local-in policies on managed devices
• Deploy out-of-band management networks so FGFM traffic never traverses untrusted segments
• Disable FortiCloud or FortiManager registration on devices that do not require centralized management until patches are applied
• Enforce strict ARP and DHCP security controls on segments carrying management traffic to reduce MITM opportunities