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Buffer Busted: FortiOS Users Urged to Patch Buffer Overflow Vulnerability

Fortinet disclosed a critical security vulnerability in its FortiOS operating system, which is CVE-2025-24477. The flaw is classified as CWE-122, a heap-based buffer overflow, and affects the cw_stad daemon, a core component responsible for wireless station management. This vulnerability enables exploitation techniques associated with T-1203, which involves execution on the client side. This blog post examines the vulnerability’s technical aspects, its potential impact, and the recommended steps to reduce the associated risk.

Root Cause

The root cause of CVE-2025-24477 lies in insufficient bounds-checking within the “cw_stad” daemon when handling incoming requests. A buffer overflow occurs when a program attempts to write more data to a buffer than is allocated, potentially overwriting adjacent memory locations. Because this overflow occurs in the heap, which is used for dynamic memory allocation, successful exploitation can lead to arbitrary code execution.

Impact & Exploit Potential

While CVE-2025-24477 has a CVSS score 4.0, its potential impact should not be underestimated. Successful exploitation could allow an attacker to control the affected FortiOS system completely. This TA0004 – Privilege Escalation could enable them to:

  • Execute arbitrary commands.
  • Install malware.
  • Modify system configurations.
  • Pivot to other systems on the network.

The requirement for authentication does reduce the likelihood of widespread exploitation. However, this vulnerability becomes a significant concern in environments where attackers have already gained initial access.

Affected Products

The CVE-2025-24477 vulnerability affects the following versions of FortiOS:

  • FortiOS 7.6.0 through 7.6.1
  • FortiOS 7.4.0 through 7.4.7
  • FortiOS 7.2.4 through 7.2.11

It’s important to note that FortiOS versions 7.0 and 6.4 are unaffected. Additionally, specific FortiWiFi models are vulnerable when configured as wireless clients. These include:

  • FWF_80F_2R_3G4G_DSL
  • FWF_80F_2R
  • FWF_81F_2R_3G4G_DSL
  • FWF_81F_2R_3G4G_POE
  • FWF_81F_2R
  • FWF_81F_2R_POE
  • FWF_90G_2R
  • FWF_91G_2R

Mitigation & Recommendations

To address CVE-2025-24477, upgrade to the following fixed versions of FortiOS:

  • FortiOS 7.6: Upgrade to 7.6.3 or above
  • FortiOS 7.4: Upgrade to 7.4.8 or above
  • FortiOS 7.2: Upgrade to 7.2.12 or above

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