CVE-2024-26659 is a vulnerability identified in the Linux kernel's xHCI (Extensible Host Controller Interface) USB driver, specifically related to the handling of isochronous (isoc) transfer events such as Babble and Buffer Overrun errors. The vulnerability arises because the xHCI 4.9 specification explicitly forbids the assumption that the host controller (xHC) has released ownership of a multi-TRB (Transfer Request Block) Transfer Descriptor (TD) when it reports an error on one of the early TRBs. However, the Linux xHCI driver incorrectly assumes this release and prematurely frees the TD. This premature release allows remaining TRBs to be freed or overwritten by new TDs, which can cause inconsistencies in transfer event processing. Additionally, the xHC should report completion of the final TRB due to its Interrupt On Completion (IOC) flag being set, regardless of prior errors. If the TD is freed early, this completion event cannot be recognized, leading to error messages such as "Transfer event TRB DMA ptr not part of current TD." The fix involves reusing logic from isochronous transaction error processing to correctly handle these error conditions and ensure proper transfer length reporting on Babble errors, which may be caused by device malfunctions and do not guarantee that the buffer has been filled. This vulnerability affects certain Linux kernel versions identified by specific commit hashes and was published on April 2, 2024. There are no known exploits in the wild at this time, and no CVSS score has been assigned yet.

For European organizations, this vulnerability in the Linux kernel's USB xHCI driver could lead to instability or denial of service conditions on systems handling USB isochronous transfers, which are commonly used for audio, video, and real-time data streams. Systems relying on USB devices for critical operations—such as industrial control systems, medical devices, or telecommunication equipment—may experience unexpected behavior or crashes if the vulnerability is triggered. Although there is no indication that this vulnerability allows for privilege escalation or remote code execution, the improper handling of transfer descriptors could be exploited by a malicious USB device or a compromised insider with physical access to cause system instability or data corruption. Given the widespread use of Linux in servers, embedded systems, and desktops across Europe, the vulnerability could affect a broad range of sectors including manufacturing, healthcare, finance, and government infrastructure. The lack of known exploits reduces immediate risk, but the vulnerability's nature suggests that attackers with physical access or supply chain compromise could leverage it to disrupt operations.

European organizations should prioritize updating their Linux kernel to the patched versions that address CVE-2024-26659 as soon as they become available. Until patches are applied, organizations should implement strict controls on physical access to systems, especially those handling sensitive or critical USB devices. Employ USB device whitelisting or disable unused USB ports to reduce the risk of malicious device insertion. For environments where isochronous USB transfers are critical, conduct thorough testing after patch deployment to ensure stability and correct operation. Additionally, monitor system logs for unusual USB-related error messages such as "Transfer event TRB DMA ptr not part of current TD," which may indicate attempts to exploit this vulnerability. Organizations should also engage with hardware vendors to verify firmware compatibility and updates that complement the kernel patch. Finally, incorporate this vulnerability into incident response plans to quickly identify and mitigate any exploitation attempts.