Fortinet Inc. (FTNT.US), a leading U.S. cybersecurity firm, saw its shares drop over 12% in after-hours trading on Wednesday after reporting weaker-than-expected service revenue growth and unexpectedly lowering its full-year 2025 revenue guidance.

The Sunnyvale, California-based company posted Q3 service revenue of $1.17 billion, up just 13% year-over-year—its slowest quarterly growth rate in at least a decade—and slightly below Wall Street estimates. Total Q3 revenue reached $1.72 billion (+14% YoY), with diluted EPS at $0.62 versus $0.70 a year earlier.

Following the earnings release, Fortinet's stock tumbled as much as 12% in extended trading. The shares had closed at $85.99 on Wednesday, up 1% for the day but only 2% year-to-date, significantly underperforming the S&P 500.

Analysts had anticipated subdued service growth due to Fortinet's limited exposure to high-growth segments like AI-driven security workloads and SASE (Secure Access Service Edge). The company also trimmed its 2025 revenue outlook, reducing the upper end of its forecast range from $6.83 billion to $6.78 billion.

Specializing in integrated "security + networking" solutions, Fortinet operates a "hardware + subscription" model with core products including FortiGate firewalls, SD-WAN, and threat protection services. While it remains a top-tier enterprise firewall provider, analysts note its lag behind peers like Palo Alto Networks and Zscaler in emerging areas such as cloud security, AI security, and XDR.