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Potential Cross-Core NoC Covert Channels on AMD Zen Processors

AMD ID: AMD-SB-7076

Summary

A researcher reported a potential cross-core covert channel on AMD Zen-based processors involving contention on the shared on-chip interconnect, or Network-on-Chip (NoC). Under certain conditions, a process generating interconnect traffic may cause measurable variations in the memory-access latency observed by a process executing on a different physical core within the same Core Complex Die (CCD). When both processes traverse an overlapping NoC path, this behavior could serve as a covert communication channel between software security domains, including between separate virtual machines on the same host.

Based on AMD’s assessment, this behavior reflects a variant of known side-channel and speculative-execution techniques rather than a new vulnerability. Existing mitigation recommendations remain applicable. Please see the Mitigation section below.

Mitigation

AMD recommends that software developers employ existing best practices, including constant-time algorithms and, where appropriate, avoiding secret-dependent control flows, to help mitigate this potential vulnerability.

Please refer to the white papers in the References section for additional guidance.

References

Software Techniques for Managing Speculation on AMD Processors (705586)
AMD CPU Timing and Power Side-Channel Guidance

Acknowledgement 

AMD thanks the following for reporting and engaging in coordinated vulnerability disclosure:

  • Externally reported by Junho Jo and Wonjun Song of Kangwon National University (KNU)

Revisions

Revision Date Description
2026-11-10 Initial version

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