Interrupt Injection Spectre v2 Bypass

Technical Analysis

The attack exploits a race condition in the timing between branch predictor sanitization routines and their subsequent use by the kernel, injecting a hardware interrupt into this narrow window to re-poison the Branch Target Buffer (BTB) or Indirect Branch Predictor before it is consumed in a trusted context. This effectively defeats existing Spectre v2 (CVE-2017-5715 class) mitigations such as IBRS, eIBRS, and retpolines that assume predictor state is clean at the point of use. Because the technique is unprivileged and works against default hardened configurations, it threatens confidentiality guarantees relied upon by multi-tenant cloud hosts, container platforms, and virtualization stacks. Hosts running LLM inference servers, agent orchestration frameworks, or RAG pipelines in shared/multi-tenant environments could have API keys, model weights, prompts, or session data leaked across process or VM boundaries via speculative side-channel reads, making this relevant to any AI agent infrastructure co-located with untrusted workloads on affected CPUs.

Affected Systems

Intel and AMD x86 CPUs vulnerable to Spectre v2 class attacks, specifically demonstrated on AMD Zen 2 processors running Linux kernel 6.14 with default Spectre v2 mitigations (IBRS/eIBRS/retpolines) enabled; likely affects broader range of Intel and AMD microarchitectures using standard branch predictor sanitization routines

Indicators of Compromise

• N/A - this is a hardware/microarchitectural side-channel research disclosure, not an active malware campaign; no file hashes, IPs, or domains associated

Remediation Steps

1. 1

   Monitor vendor advisories

   Track Intel, AMD, and Linux kernel security advisories for official microcode and kernel patches addressing the Interrupt Injection technique.

2. 2

   Apply kernel updates

   Deploy Linux kernel patches once released that close the timing gap between branch predictor sanitization and kernel use of indirect branches.

3. 3

   Update CPU microcode

   Apply vendor-issued microcode updates for affected Intel and AMD processors as they become available.

4. 4

   Harden multi-tenant environments

   For cloud and virtualization hosts running AI agent workloads alongside untrusted tenants, consider disabling hyperthreading, enforcing core scheduling, and isolating sensitive workloads on dedicated hardware until patches are available.

5. 5

   Audit AI infrastructure exposure

   Identify LLM inference and agent orchestration hosts running in shared or multi-tenant environments and prioritize patching or isolation for these systems given potential exposure of API keys and model data.