From Colocation to Exfiltration: Practical Cache Side-Channel Attacks in the Modern Public Cloud

Sharing resources among tenants is fundamental to public clouds, enhancing efficiency but also creating opportunities for microarchitectural side-channel attacks. However, cloud vendors remain skeptical about the practicality of these attacks, particularly regarding the ability to colocate attacker and victim, and to overcome system noise. In this work, we develop a series of techniques for each step of the attack and, for the first time, demonstrate cross-tenant information leakage on the public Google Cloud Run, refuting the belief that such attacks are impractical. Our findings highlight the need to secure public clouds against side-channel attacks.