The Trusted Platform Module (TPM) 2.0 specification is affected by two buffer overflow vulnerabilities that could allow attackers to access or overwrite sensitive data, such as cryptographic keys.

TPM is a hardware-based technology that provides operating systems with tamper-proof secure cryptographic functions. It can be used to store cryptographic keys, passwords, and other critical data, making any vulnerabilities in its implementation a concern.

Although a TPM is required for certain Windows security features, such as Measured Boot, Device Encryption, Windows Defender System Guard (DRTM), Device Health Attestation, it does not is not required for other more commonly used features.

However, when a Trusted Platform Module is available, Windows security features get enhanced security by protecting sensitive information and encrypting data.

The TPM 2.0 specification gained popularity (and controversy) when Microsoft made it a requirement to run Windows 11 due to its required startup security measures and ensuring that Windows Hello facial recognition provides strong authentication.

Linux also supports TPMs, but there is no requirement for using the module in the operating system. However, there is Linux tools available that enable applications and users to secure data in TPMs.

TPM 2.0 vulnerabilities

The new TPM 2.0 vulnerabilities were discovered by Quarkslab researchers Francisco Falcon and Ivan Arce, who said the flaws could impact billions of devices. The vulnerabilities are tracked as CVE-2023-1017 (read out of bounds) and CVE-2023-1018 (write out of bounds).

Both flaws stem from the way the specification handles the parameters of certain TPM commands, allowing an authenticated local attacker to exploit them by sending maliciously crafted commands to execute code in the TPM.

According to safety bulletin by Trusted Computing Group (TCG), the developer of the TPM specification, this could result in disclosure of information or elevation of privilege.

The Trusted Computing Group explains that buffer overflow issues relate to reading or writing 2 bytes past the end of the buffer passed to the ExecuteCommand() entry point.

The impact of this depends on what the vendors have implemented on that memory location, i.e. if it is unused memory or if it contains live data.

The CERT Coordination Center issued an alert about the vulnerabilities and has been advising vendors for months, trying to raise awareness while mapping the impact. Unfortunately, only a handful of entities have confirmed that they are affected.

“An attacker who gains access to a TPM command interface can send maliciously crafted commands to the module and trigger these vulnerabilities,” CERT aware.

“This allows either read-only access to sensitive data or the overwriting of normally protected data that is only available to the TPM (e.g. cryptographic keys).”

The solution for affected vendors is to move to a fixed version of the specification, which includes one of the following:

• TMP 2.0 v1.59 Errata version 1.4 or higher
• TMP 2.0 v1.38 Errata version 1.13 or higher
• TMP 2.0 v1.16 Errata version 1.6 or higher

Lenovo is the only major OEM to release a security consulting on the two TPM flaws so far, warning that CVE-2023-1017 is impacting some of its systems running on Nuvoton TPM 2.0 chips.

Although these flaws require authenticated local access to a device, it is important to remember that malware running on the device meets this requirement.

The TPM is a highly secure space that should theoretically be protected even against malware running on the device, so the practical significance of these vulnerabilities should not be ignored or minimized.

It is recommended that users limit physical access to their devices to trusted users, only use signed applications from reputable vendors, and apply firmware updates as soon as they are available for their devices.