CacheBleed: A Timing Attack on OpenSSL Constant Time RSA
FYI, for those are just worried about their own servers, the important part is section five, which I have copied below:<p>-------------------------------------<p>Q5: Should normal users or system administrators be worried?<p>OpenSSL has classified this vulnerability as "low severity", which we agree with. In order to mount the attack, the attacker has to be able to run the attack code on the same machine that runs the victim code. CacheBleed is a complex attack and there are much easier-to-exploit vulnerabilities in personal computers that it is unlikely that anyone would use CacheBleed in such an environment.<p>Cloud servers that commonly run mutually untrusting workloads concurrently are a more realistic attack scenario. A malicious client of a cloud service could use the CacheBleed attack to spy on other clients. While cloud servers employ techniques to isolate workloads of different clients from one another, these techniques only isolate the software and do not prevent hardware-based attacks, such as CacheBleed. Nevertheless, due to the complexity of the attack and its sensitivity to system noise we believe it is not currently a practical risk to cloud environments.<p>The attack only works between processes running on two hyper-threads of the same core. Disabling hyper-threading is an effective mitigation against the attack.