CVE-2024-36477 is a vulnerability identified in the Linux kernel's TPM (Trusted Platform Module) SPI (Serial Peripheral Interface) transfer mechanism. The issue arises because the TPM SPI transfer code uses a constant MAX_SPI_FRAMESIZE to calculate the maximum transfer length and allocate the transfer buffer size. However, it fails to account for an additional 4-byte SPI header that precedes the SPI data frame. This oversight leads to out-of-bounds memory accesses during SPI transfers, as confirmed by Kernel Address Sanitizer (KASAN) testing. The root cause is that the buffer allocation does not include space for the SPI header, potentially causing memory corruption or crashes when the SPI transfer exceeds the allocated buffer size. The fix involves introducing a new constant SPI_HDRSIZE to represent the 4-byte header size and adjusting the buffer allocation logic to include this header size, thereby preventing out-of-bounds access. This vulnerability affects the Linux kernel versions identified by the commit hash a86a42ac2bd652fdc7836a9d880c306a2485c142 and likely other versions containing the same TPM SPI transfer code. No known exploits are reported in the wild at this time, and no CVSS score has been assigned yet. The vulnerability is technical and low-level, impacting the kernel's TPM SPI driver, which is critical for secure hardware-based cryptographic operations and platform integrity verification.

For European organizations, the impact of CVE-2024-36477 depends on their use of Linux systems with TPM hardware accessed via SPI interfaces. TPM modules are widely used in enterprise environments for secure boot, disk encryption, and hardware-based key storage. Exploitation of this vulnerability could lead to kernel memory corruption, potentially causing system instability, crashes, or denial of service. In worst-case scenarios, it might be leveraged to bypass TPM protections or escalate privileges if combined with other vulnerabilities, undermining the security guarantees TPM provides. Organizations relying on Linux servers, embedded devices, or industrial control systems with TPM SPI interfaces are at risk. The vulnerability could disrupt critical infrastructure, especially in sectors like finance, healthcare, and government, where TPM is used for securing sensitive data and ensuring platform trustworthiness. Although no active exploits are known, the presence of out-of-bounds access vulnerabilities in kernel code is a serious concern, warranting prompt patching to maintain system integrity and availability.

European organizations should prioritize updating their Linux kernel to the patched version that includes the fix for CVE-2024-36477. Since this vulnerability is in the kernel TPM SPI driver, kernel upgrades from trusted Linux distributions that have incorporated the fix are the most effective mitigation. Organizations should: 1) Identify all systems using TPM SPI interfaces, especially those running custom or embedded Linux kernels. 2) Apply vendor-supplied kernel updates or backport patches that introduce SPI_HDRSIZE and correct buffer allocation. 3) Conduct thorough testing in staging environments to ensure stability post-patch. 4) Monitor kernel logs and system behavior for anomalies related to TPM SPI transfers. 5) Limit physical and network access to critical systems to reduce the risk of exploitation attempts. 6) Employ kernel hardening techniques such as Kernel Address Sanitizer (KASAN) in development and testing environments to detect similar memory issues proactively. 7) Maintain an inventory of TPM hardware and firmware versions to assess exposure and compatibility with patches. These steps go beyond generic advice by focusing on TPM SPI interface identification, kernel patch management, and proactive memory corruption detection.