CVE-2021-3505

A flaw was found in libtpms. The TPM 2 implementation returns 2048 bit keys with ~1984 bit strength due to a bug in the TCG specification. The bug is in the key creation algorithm in RsaAdjustPrimeCandidate(), which is called before the prime number check. The highest threat from this vulnerability is to data confidentiality.

Mitigation

There is no mitigation for this issue. Upgrading to a fixed release (0.8.0+) is necessary but not sufficient. The only way to fix it is to unseal all data, delete the old TPM state file, generate a new one with the fixed key generation algorithm, then reseal the data.