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hß · SecurityCurated

The security coprocessor in many CPUs is insecure

Summary

In August 2026 two holes became known in the Trusted Computing Group’s reference code for firmware TPMs (fTPM 2.0), which AMD and Intel adopt in their BIOS versions. CVE-2026-6727 is a timing side channel in RSA-OAEP; CVE-2026-6726 allows discarded keys to be replaced by false ones. They can only be exploited with local, privileged access and are mainly relevant for company devices.

Ideas

  • Firmware TPMs run as firmware on an isolated core of the CPU.
  • A bug in the shared reference code hits many manufacturers at once.
  • Different response times for correct and incorrect padding give away secrets.
  • Keys that are not correctly invalidated can be replaced by forged ones.

Insights

  • The chain of trust is only as strong as its first link.
  • The lack of certification for fTPMs left flaws unnoticed for longer than with discrete TPM chips.

Facts

  • The holes have CVSS scores of 8.5 and 8.3.
  • According to the report, all AMD Zen processors from Ryzen 1000 to Ryzen 9000 are affected.
  • Certifications such as CC EAL 4+ only exist for discrete TPM chips.
  • At Intel, client processors up to the Core Ultra 200 series are affected, and among servers Xeon Scalable up to Ice Lake.
  • Besides BIOS updates there are software patches, for example for the Linux library libtpms.

References

Critique

  • The report does not say how many requests the timing attack needs and how long it takes.

Recommendations

  • Apply BIOS updates with fixed fTPM firmware on company devices promptly.
  • For systems that need particular protection, use a certified discrete TPM chip.

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