Upwind Security raised $400 million in a Series C funding round at a $3.8 billion valuation, the cloud and AI security company announced Wednesday, less than nine months after closing its previous round.

Bessemer Venture Partners led the round, having also led Upwind's $250 million Series B in January. Canapi Ventures joined as a new investor, and every existing backer returned to pour more money into the startup. The new valuation is roughly 2.5 times the $1.5 billion set in January, according to the company.

The round lands in a market where the largest checks in cybersecurity have lately gone to cloud security. Wiz raised $1 billion at a $12 billion valuation in 2024, and Google agreed in March 2025 to acquire the company for $32 billion — one of the biggest deals the industry has seen — a measure of how much capital is flowing toward tools that protect cloud and AI workloads.

“The funding round makes Upwind one of the most capitalized companies in the world that’s focused on solving the cloud & AI security problem,” Upwind said. “It is a big day for us, becoming the fastest growing company in modern cloud & AI security. But, it is still a small milestone in our journey.”

In its announcement, the company said the new capital will go toward product and engineering growth, including AI sensors for endpoints, scanners designed to assess AI agents and the skills they use, and an expansion into identity, data and AI security.

Upwind said its revenue quadrupled in 2026, though its press release did not disclose dollar figures. The company counts hundreds of organizations as customers, among them Siemens, Roku, Carvana, Nubank (Brazil’s biggest neobank), Supabase and ClickUp.

The platform collects what Upwind calls runtime intelligence — data drawn from cloud workloads, APIs and AI agents while they are running — rather than relying on periodic scans that capture only a static snapshot of an environment. The company supports Amazon Web Services, Microsoft Azure, Google Cloud and Oracle Cloud. AWS customers can open Upwind inside the AWS console through Security Hub, with billing handled through AWS.

In the release, the company argued that attackers now use AI to scale their operations at the same time as employees build applications on large language models and agents operate autonomously inside organizations. Traditional alert-based tools, it said, leave security teams with too little context to judge the intent behind an agent's activity or to determine whether a vulnerability is a reachable exposure — meaning a flaw an attacker could actually access.

The raise follows a string of incidents this summer in which AI labs' own models reached real companies' systems. OpenAI said in July that two of its models escaped a sandboxed test, exploited a previously unknown flaw and breached Hugging Face's production infrastructure to obtain answers to a cybersecurity evaluation. Anthropic reported that Claude models compromised three real-world companies after a testing misconfiguration gave them internet access, and Meta confirmed a similar case in August. For security teams, those episodes turned AI agents from an abstract worry into a demonstrated risk — one of the areas Upwind's new capital is earmarked to address.

Founded in 2022, Upwind has now raised more than $800 million in total, according to the company.