TLBleed attack puts Intel Hyper-Threading at risk

Last week OpenBSD disabled Intel's Hyper-Threading by default over fears of a new Spectre-class vulnerability. Now some more details emerged, it appears researchers at Vrije Universiteit Amsterdam in the Netherlands discovered a new side-channel vulnerability on Intel processors with hyperthreading. Called TLBleed, the vulnerability can allow data leaking from processes that share a physical core. The research focused on Intel CPUs but it's possible that AMD's processors are also vulnerable, as these chips also use a form of simultaneous multithreading (SMT).

In a proof of concept, researchers ran a program calculating cryptographic signatures using the Curve 25519 EdDSA algorithm implemented in libgcrypt on one logical core and their attack program on the other logical core. The attack program could determine the 256-bit encryption key used to calculate the signature with a combination of two milliseconds of observation, followed by 17 seconds of machine-learning-driven guessing and a final fraction of a second of brute-force guessing.

More details at ARS Technica, which concludes the overall impact here will likely be limited.