Rein Security Raises $25 Million to Secure the AI Agents Enterprises Build and Stop the Ones That Attack Them

Glilot Capital and Sienna Venture Capital Co-Lead Series A Round, Bringing Total Funding Secured to Date to $35 Million

NEW YORK and TEL AVIV, Israel, Oct. 8, 2026 /PRNewswire/ -- Rein Security, the AI-native runtime security platform for enterprises, today announced that the company has raised $25 million in Series A financing, bringing the company's 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.

The funding comes as enterprises rapidly deploy AI agents with increasingly broad access to business systems, data and workflows, creating a new class of security risks that traditional approaches were not designed to detect or stop. According to Gartner, the market for securing AI is projected to reach nearly $4.8 billion in 2027, up 68.7% from 2026, and nearly $7.7 billion by 2028. As AI agent adoption accelerates and agents become increasingly autonomous, enterprises face two security challenges at once, securing the agents they build while defending against increasingly capable AI-driven attacks.

Rein addresses both sides of this challenge. Its platform is built on patented sidecar technology that operates at runtime, at the point where agents execute actions. This gives security teams visibility into every line of code an agent runs and every resource it touches, along with governance over agent activity and real-time guardrails that block harmful actions. Rein also secures the agent supply chain, all without routing company or customer data through a gateway or proxy.

"Enterprise AI agents are becoming essential to how businesses operate, but security hasn't kept pace with the autonomy these systems now have," said Matan Bar-Efrat, co-founder and CEO of Rein Security. "This funding enables us to keep building the infrastructure enterprises need to deploy AI agents with visibility, control and confidence."

Enterprises are adopting AI agents faster than they can secure them, and most of the risk these agents create is both new and hidden. It sits in the downstream actions they take automatically across business systems, often on instructions passed along by another system or agent rather than a person. Securing agents means understanding every action they take and stopping harmful ones. The same is true of adversarial AI, which attacks at machine speed and can overwhelm security teams. This calls for a completely different strategy: shifting focus away from posture and vulnerability management to a more proactive approach that prioritizes prevention and protection. 

"The agent economy is upon us, and the rapid adoption of AI agents is creating a fundamental shift in enterprise security," said Arik Kleinstein at Glilot Capital. "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."

The risks Rein uncovers are already appearing in production environments. For example, at Black Hat USA 2026, Rein's vulnerability research team, Agent Breakers, presented research showing how it compromised the AI shopping agent of a top-five U.S. retailer. The work showed how quickly AI adoption is outpacing security. Furthermore, a global enterprise's onboarding agent opened what looked like an ordinary PDF. Hidden inside was a prompt injection that directed the agent to act outside its intended role. Rein detected and blocked the action before any damage was done.

"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," said Thomas Visan at Sienna Venture Capital. "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."

Answering the Call for Stronger Agentic AI Protection 

Amid a period of significant revenue and customer growth, Rein will use the new capital to accelerate product innovation, advance agentic research and support global hiring. Since its January 2026 launch, Rein has increased revenue by 8x and grown its customer base by 5x.

New customers, including Flex and Swimlane, broaden Rein's reach across industries including financial services, healthcare, SaaS, data, retail and energy.

As enterprises build and deploy increasingly capable AI agents, Rein is seeing growing demand for security that can keep pace with agent adoption. The company's platform is already securing thousands of AI agents that execute millions of actions, including Dun & Bradstreet and digital-first insurance leader, Lemonade. Rein protects AI agents for Lemonade, supporting services used by over three million active customers; as well as agents for Dun & Bradstreet, powering agentic products used by more than 240,000 customers.

"Our customers rely on Dun & Bradstreet for trusted data, and that trust has to extend to every AI agent we put into production," said Jay DePaul, chief cybersecurity & technology risk officer at Dun & Bradstreet. "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."

Rein has also earned recognition from the broader technology and cybersecurity community in recent months. The company was selected as one of eight early-stage companies to compete in the AI Conference's Start Up Showdown and was named to TechCrunch's Startup Battlefield 200 as one of the most promising early-stage startups in the cybersecurity category.

For more information, visit www.reinsec.io.

About Rein Security:
Rein Security is the agentic AI security company purpose-built for enterprise agents. With a patented, real-time architecture, Rein delivers full visibility and protection across every enterprise agent – tracing every action to the line of code that triggered it and connecting it to its business outcome. Trusted by leading Fortune 500 companies and backed by Glilot Capital, Sienna Venture Capital, and Corner Ventures, Rein Security was founded in 2024 and is co-headquartered in New York City and Tel Aviv.

Media Contact:
Bateman Agency for Rein Security
[email protected] 

SOURCE Rein Security, Inc.