CVE-2024-26677 is a vulnerability identified in the Linux kernel specifically related to the rxrpc protocol implementation. The issue concerns the handling of delayed ACKs (acknowledgments) within the rxrpc protocol, where the construction of these delayed ACKs incorrectly sets the reference serial number. This reference serial number is used for Round-Trip Time (RTT) measurement, and setting it incorrectly can lead to inaccurate RTT calculations. The vulnerability fix involves modifying the delayed ACK construction logic to avoid setting the reference serial number, as delayed ACKs are not suitable for RTT reference. While the description does not explicitly state the exploitation method or the direct impact, the flaw lies in the protocol's internal timing and acknowledgment mechanisms, which could potentially be leveraged to disrupt communication reliability or performance. The vulnerability affects the Linux kernel, which is widely used across numerous distributions and environments, including servers, desktops, and embedded systems. No known exploits are reported in the wild as of the publication date, and no CVSS score has been assigned yet. The vulnerability was reserved in February 2024 and published in April 2024, indicating recent discovery and patching efforts.

For European organizations, the impact of CVE-2024-26677 depends largely on the deployment of Linux systems using the rxrpc protocol, which is commonly associated with certain RPC (Remote Procedure Call) services, including some implementations related to AFS (Andrew File System) and other distributed systems. If exploited, the vulnerability could lead to inaccurate RTT measurements, potentially causing degraded network performance, delayed acknowledgments, or instability in services relying on rxrpc. This could affect critical infrastructure, enterprise servers, and cloud environments running Linux kernels vulnerable to this issue. While no direct evidence suggests privilege escalation or remote code execution, the disruption of network communication could impact availability and reliability of services, which is critical for sectors such as finance, healthcare, telecommunications, and government services in Europe. The absence of known exploits reduces immediate risk, but organizations should remain vigilant given the widespread use of Linux and the potential for attackers to develop exploits targeting this kernel-level flaw.

To mitigate CVE-2024-26677, European organizations should prioritize updating their Linux kernel to the latest patched versions provided by their distribution vendors as soon as possible. Since the vulnerability is kernel-level, applying official kernel patches or upgrading to a kernel version that includes the fix is essential. Organizations should audit their environments to identify systems running Linux kernels affected by this issue, particularly those using rxrpc-dependent services. Network monitoring should be enhanced to detect anomalies in RPC traffic patterns that could indicate exploitation attempts. Additionally, organizations should review and harden RPC-related configurations, limit exposure of vulnerable services to untrusted networks, and employ network segmentation to reduce attack surfaces. For critical systems, consider implementing kernel live patching solutions to minimize downtime while applying fixes. Finally, maintain up-to-date incident response plans to quickly address any potential exploitation attempts.