Horizon3 Secures $250M Series E, Valuation Exceeds $2B

Cybersecurity firm Horizon3 has raised $250 million in a Series E funding round, valuing the company at more than $2 billion and more than tripling its valuation from approximately $650 million in just over a year. The oversubscribed round, announced on August 3, 2026, was co-led by existing investors NightDragon and New Enterprise Associates (NEA), with participation from several new and returning backers.

The San Francisco-based startup, founded in 2019, specializes in autonomous penetration testing. Its flagship platform, NodeZero, uses artificial intelligence to continuously probe and attack a customer’s own live production networks to find security weaknesses, simulating the methods of a real intruder without causing operational disruptions. The platform then provides guidance on how to fix the vulnerabilities and re-tests to confirm they are resolved.

Company executives framed the massive capital infusion as a response to an accelerating threat landscape, where AI-driven attacks are outpacing traditional, human-centric defenses. CEO Snehal Antani stated that the future of cyber warfare is fundamentally AI fighting AI, with humans operating by exception. The company says...