Fallout: Leaking Data on Meltdown-resistant CPUs

Claudio Alberto Canella, Daniel Genkin, Lukas Giner, Daniel Gruß, Moritz Lipp, Marina Minkin, Daniel Moghimi, Frank Piessens, Michael Schwarz, Berk Sunar, Jo Van Bulck, Yuval Yarom

Research output: Chapter in Book/Report/Conference proceedingConference paperpeer-review


Meltdown and Spectre enable arbitrary data leakage from memory via various side channels. Short-term software mitigations for Meltdown are only a temporary solution with a significant performance overhead. Due to hardware fixes, these mitigations are disabled on recent processors.

In this paper, we show that Meltdown-like attacks are still possible on recent CPUs which are not vulnerable to Meltdown. We identify two behaviors of the store buffer, a microarchitectural resource to reduce the latency for data stores, that enable powerful attacks. The first behavior, Write Transient Forwarding forwards data from stores to subsequent loads even when the load address differs from that of the store. The second, Store-to-Leak exploits the interaction between the TLB and the store buffer to leak metadata on store addresses. Based on these, we develop multiple attacks and demonstrate data leakage, control flow recovery, and attacks on ASLR. Our paper shows that Meltdown-like attacks are still possible, and software fixes with potentially significant performance overheads are still necessary to ensure proper isolation between the kernel and user space.
Original languageEnglish
Title of host publicationCCS 2019 - Proceedings of the 2019 ACM SIGSAC Conference on Computer and Communications Security
Number of pages15
ISBN (Electronic)978-1-4503-6747-9
Publication statusPublished - 12 Nov 2019
Event26th ACM Conference on Computer and Communications Security: ACM CCS 2019 - London, United Kingdom
Duration: 11 Nov 201915 Nov 2019


Conference26th ACM Conference on Computer and Communications Security
Country/TerritoryUnited Kingdom


  • side-channel attack
  • Meltdown
  • Spectre
  • store buffer
  • store-to-load


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