MIT boffins' TONTOU attack slips through Spectre defenses on Intel and AMD CPUs
- ID
- 11970
- Status
- summarized
- Published
- 07 Aug 2026, 10:15 PM
- Fetched
- 07 Aug 2026, 10:56 PM
- Provider
- The Register
- Category
- technology
- Original URL
- https://www.theregister.com/security/2026/08/07/mit-boffins-tontou-attack-slips-through-spectre-defenses-on-intel-and-amd-cpus/5284081
- Source URL
- https://www.theregister.com/headlines.atom
Summary
- Score
- 5.5
- Created
- 07 Aug 2026, 10:57 PM
- Tags
- Audience
- developerssaas_founders
What happened
MIT CSAIL researchers Daniël Trujillo and Mengjia Yan will present TONTOU at DEF CON 34, a new speculative execution attack that bypasses Spectre v2 defenses on Intel and AMD CPUs by using precisely timed timer interrupts to re-poison branch predictor state during the post-neutralization window. They demonstrated a working exploit on AMD Zen 2 using a stock Linux kernel with all default mitigations enabled, showing that both Intel's eIBRS (entry neutralization) and AMD's Safe RET (in-place neutralization) are vulnerable.
Why it matters
If you operate multi-tenant infrastructure on Intel or AMD CPUs—especially Zen 2—unprivileged code with timer access can re-poison branch predictor state after mitigations run, meaning existing Spectre v2 defenses are insufficient until kernel or microcode patches land. Cloud providers will likely patch transparently, but anyone self-hosting shared workloads should track vendor advisories and plan for kernel updates rather than assuming current eIBRS or Safe RET protections are adequate.
Discussion angle
For most of us on managed cloud, this is the provider's problem—but if you're running your own KVM hosts or bare-metal multi-tenant setups, the gap between 'mitigations enabled' and 'actually safe' is the thing to discuss, and whether it changes any build-vs-buy calculus for infrastructure.