CVE-2021-47668: 
Linux Kernel vulnerability analysis and mitigation

CVE-2021-47668 is a use-after-free vulnerability discovered in the Linux kernel's CAN (Controller Area Network) subsystem. The vulnerability was disclosed on April 17, 2025, affecting multiple versions of the Linux kernel from 2.6.31 through 5.10.11 (NVD).

The vulnerability occurs in the canrestart function where after calling netifrxni(skb), the code unsafely dereferences the skb. Specifically, the canframe cf which aliases skb memory is accessed after the netifrxni() call in the statement: stats->rx_bytes += cf->len. The vulnerability has been assigned a CVSS v3.1 base score of 7.8 (HIGH) with the vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H and is classified as CWE-416 (Use After Free) (NVD).

The vulnerability could potentially lead to high-severity impacts on confidentiality, integrity, and availability of the affected systems, as indicated by the CVSS scoring. The local attack vector suggests that an attacker would need local system access to exploit this vulnerability (NVD).

The issue has been fixed in multiple Linux kernel versions. Debian has released fixes in versions 5.10.223-1 for bullseye, 6.1.129-1 for bookworm, and 6.12.22-1 for trixie. The fix involves reordering the code lines to prevent the use-after-free condition (Debian).