The vulnerability exists in the Linux kernel's nftables module. During packet filtering rule initialization the library accepts shift operators with a zero shift value. The kernel then performs a 32-bit shift operation to propagate carry bits, which is undefined behaviour and can corrupt the kernel's internal state. Maliciously crafted nftables rules that use a zero shift can trigger a kernel crash or denial‑of‑service condition, potentially affecting the entire operating system. The weakness is an input validation failure and a failure to guard against undefined behaviour (CWE‑1335) in the control plane of the nft_bitwise expression.

All Linux kernels that implement the nft_bitwise expression without the new zero‑shift check are affected. The vulnerability is not limited to a single vendor; it applies to every distribution that ships the affected kernel code. The precise kernel version that was patched is not specified in the advisory.

The EPSS score of < 1% indicates a very low probability of exploitation in the wild. The CVSS score of 5.5 reflects moderate severity for a kernel‑level flaw that can cause a crash. The vulnerability is not listed in CISA KEV, so no known widespread exploitation has been reported. The likely attack vector is local for users who can modify nftables rules, or remote if an attacker gains such privilege. Because the bug is confined to the control plane and must be triggered during rule compilation, it is a low‑effort denial of service flaw that requires the attacker to supply a crafted rule.