Certain function pointers in Trusted Boot (tboot) through 1.9.6 are not validated and can cause arbitrary code execution, which allows local users to overwrite dynamic PCRs of Trusted Platform Module (TPM) by hooking these function pointers.
https://www.usenix.org/conference/usenixsecurity18/presentation/han
https://sourceforge.net/p/tboot/code/ci/521c58e51eb5be105a29983742850e72c44ed80e/