CVE-2024-56688: 
Linux Kernel vulnerability analysis and mitigation

CVE-2024-56688 is a vulnerability in the Linux kernel's sunrpc (Sun Remote Procedure Call) implementation, discovered and disclosed on December 28, 2024. The vulnerability affects Linux kernel versions from 4.11 up to versions before 5.4.287, 5.10.231, 5.15.174, and 6.1.120. The issue occurs in the transport socket handling where XPRT_SOCK_UPD_TIMEOUT flag is not properly cleared when resetting transport (NVD).

The vulnerability stems from a NULL pointer dereference issue in the Linux kernel's sunrpc implementation. When the transport->sock is set to NULL during reset transport, the XPRT_SOCK_UPD_TIMEOUT flag is not cleared properly. This can lead to xs_tcp_set_socket_timeouts() being triggered in xs_tcp_send_request(), causing a dereference of the NULL transport->sock pointer. The vulnerability has been assigned a CVSS v3.1 base score of 5.5 (Medium) with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (NVD).

The vulnerability can lead to a system crash due to NULL pointer dereference when the sunrpc transport socket is being reset. This primarily affects system availability, as indicated by the CVSS metrics showing no impact on confidentiality or integrity, but high impact on availability (NVD).

The vulnerability requires local access and low privileges to exploit, as indicated by the CVSS metrics (AV:L/AC:L/PR:L/UI:N). No user interaction is required for exploitation once an attacker has the necessary local access (NVD).

The vulnerability has been patched in the Linux kernel. The fix involves adding code to clear the XPRT_SOCK_UPD_TIMEOUT flag when resetting transport. The patch has been applied to multiple kernel versions and is available in the kernel stable tree. Ubuntu has released fixes for version 6.11.0-18.18 in 24.10 (oracular) and various other distributions are in the process of releasing updates (Kernel Patch).