A flaw was found in tpm2-tss, which is an open source software implementation of the Trusted Computing Group (TCG) Trusted Platform Module (TPM) 2 Software Stack (TSS2). In affected versions, `Tss2_RC_SetHandler` and `Tss2_RC_Decode` index into the `layer_handler` with an 8-bit layer number, but the array only has `TPM2_ERROR_TSS2_RC_LAYER_COUNT` entries. Trying to add a handler for higher-numbered layers or to decode a response code with a layer number, reads/writes past the end of the buffer. This buffer overrun could result in arbitrary code execution. An example attack is a man-in-the-middle (MiTM) bus attack that returns 0xFFFFFFFFFF for the RC. Given the common use case of TPM modules, an attacker must have local access to the target machine with local system privileges, which allows access to the TPM system. Usually, TPM access requires administrative privileges.