Artificial intelligence is reshaping cyber risk in the financial sector by accelerating the speed, frequency, and breadth of vulnerability discovery and potential exploitation. As AI becomes more deeply embedded in financial institutions and market infrastructures, it can strengthen cyber defense but also heighten systemic risk—particularly through shared digital infrastructure, common service providers, and machine-speed attack-defense dynamics that outpace human response. This note argues that the main financial stability concern lies less in new types of cyberattacks than in the scale effects AI can unleash across common technologies, amplifying how quickly and widely risks spread. Strong governance and technical controls that limit the “blast radius” of breaches—that is, the scope of damage they can cause—and effectively contain their spread, robust response and recovery capacity, and stronger international coordination will be essential to safeguard financial stability. A whole-of-nation approach, bringing together government, the private sector, and other stakeholders, is warranted given the cross-sector implications, limited private incentives for adequate cyber risk management, and benefits of public-private collaboration.