Rein Security, an AI-native runtime security platform focused on enterprise AI agents, raised $25 million in Series A funding, bringing its total funding to $35 million. The round was co-led by Glilot Capital and Sienna Venture Capital, with participation from Corner Ventures, Atlacle, and RNP Capital Advisors.
Rein plans to use the new capital to accelerate product development, expand its agentic AI security research, and support global hiring as enterprises increase their deployment of autonomous AI agents.
Founded in 2024 and co-headquartered in New York City and Tel Aviv, Rein develops security infrastructure designed to help enterprises secure both the AI agents they deploy internally and defend against AI-powered attacks.
The company’s platform uses patented sidecar technology that operates at runtime, where AI agents execute actions across business systems, data, and workflows.
This architecture gives security teams visibility into the code agents execute and the resources they access while enabling real-time governance and controls intended to block potentially harmful activity.
Rein also provides protection across the AI agent supply chain without requiring enterprises to route company or customer data through a gateway or proxy.
The company is positioning its technology around a growing security challenge created by increasingly autonomous AI systems. As agents receive broader permissions to interact with enterprise applications, make decisions, and perform tasks without continuous human intervention, organizations can face risks that traditional cybersecurity tools were not designed to address.
Rein said these risks can emerge from downstream actions initiated automatically by AI agents, including actions triggered by instructions originating from other applications or agents rather than directly from a person.
The company is also focused on defending enterprises from adversarial AI systems capable of launching attacks at machine speed.
According to Gartner figures cited by Rein, the market for securing AI is expected to reach nearly $4.8 billion in 2027, representing growth of 68.7% from 2026, before reaching nearly $7.7 billion in 2028.
Rein launched commercially in January 2026 and said it has since increased revenue by 8x while expanding its customer base by 5x.
The company’s customers include Flex, Swimlane, Dun & Bradstreet, and Lemonade, with deployments spanning industries including financial services, healthcare, SaaS, data, retail, and energy.
Rein said its platform is currently securing thousands of AI agents responsible for executing millions of actions.
At Lemonade, Rein protects AI agents supporting services used by more than three million active customers. At Dun & Bradstreet, the platform helps secure agents supporting agentic products used by more than 240,000 customers.
Rein has also been conducting vulnerability research through its Agent Breakers research team.
At Black Hat USA 2026, the team presented research showing how it compromised an AI shopping agent used by a major U.S. retailer, illustrating potential vulnerabilities created as companies rapidly deploy agentic systems.
In another example cited by the company, an enterprise onboarding agent encountered a PDF containing a hidden prompt injection designed to instruct the agent to operate outside its intended role. Rein said its platform detected and blocked the resulting action.
The company has also received recognition from the broader startup and cybersecurity ecosystem. Rein was selected as one of eight early-stage companies participating in the AI Conference’s Start Up Showdown and was included in TechCrunch’s 2026 Startup Battlefield 200 in the cybersecurity category.
KEY QUOTES:
“Enterprise AI agents are becoming essential to how businesses operate, but security hasn’t kept pace with the autonomy these systems now have. This funding enables us to keep building the infrastructure enterprises need to deploy AI agents with visibility, control and confidence.”
Matan Bar-Efrat, Co-Founder and CEO of Rein Security
“The agent economy is upon us, and the rapid adoption of AI agents is creating a fundamental shift in enterprise security. As agents gain the ability to access systems, make decisions and act autonomously, enterprises need a new approach built specifically for this new landscape. This is a fast-moving and underserved area of security, and Rein has the platform, vision and early traction to help define it.”
Arik Kleinstein, Glilot Capital
“As an enterprise’s technology ecosystem grows and evolves to include more AI agents that have a direct impact in production environments, security becomes an even greater concern. The frameworks that exist today are simply not equipped to handle this transition. Rein’s differentiated platform explicitly addresses current, as well as new, agentic AI security threats, giving the company a distinct position in this rapidly evolving market.”
Thomas Visan, Sienna Venture Capital
“Our customers rely on Dun & Bradstreet for trusted data, and that trust has to extend to every AI agent we put into production. Rein helps us see and control what our agents do at scale, so we can keep innovating with agentic AI while protecting the customers who depend on it.”
Jay DePaul, Chief Cybersecurity & Technology Risk Officer at Dun & Bradstreet
