CVE-2023-53667: 
Linux Kernel vulnerability analysis and mitigation

A vulnerability has been identified in the Linux kernel's cdc_ncm driver, tracked as CVE-2023-53667. The issue was discovered and disclosed on October 7, 2025, affecting the network subsystem's handling of dwNtbOutMaxSize values in the USB CDC NCM driver (Ubuntu Security, Red Hat Security).

The vulnerability exists in the cdcncmchecktxmax() function where if dwNtbOutMaxSize is lower than the calculated 'min' value but greater than zero, the logic sets txmax to dwNtbOutMaxSize. This value is then used to allocate a new SKB in cdcncmfilltx_frame(). Due to memory alignment during allocation, small values of dwNtbOutMaxSize can lead to insufficient space for CDC data when SKB header structs increase in size, potentially causing buffer overflow conditions (Ubuntu Security).

When exploited, this vulnerability can lead to kernel memory corruption and system crashes. The issue manifests when the CDC data no longer fits in the spare SKB data area due to size mismatches, resulting in SKB bounds checking failures and kernel panics (Red Hat Security).

The issue has been fixed by clamping dwNtbOutMaxSize values to the range [USBCDCNCMNTBMINOUTSIZE, CDCNCMNTBMAXSIZE_TX]. This ensures sufficient data space is allocated to handle CDC data by enforcing a minimum size requirement. Multiple Linux distributions have released patches, including Ubuntu which has fixed the issue in various kernel versions (Ubuntu Security).