The vulnerability resides in the xt_connmark target of the Linux kernel’s netfilter subsystem, where revision 2 accepts user‑controlled shift parameters without validation. This allows attackers to supply shift values that are incorrect or exceed the allowed range. When a shift value of 32 or more is specified, the kernel performs an undefined‑shift operation that can corrupt memory or trigger a panic during packet processing, potentially leading to system instability or a crash. The flaw also silently accepts invalid shift directions, allowing a malicious rule to be installed without immediate detection.

All Linux kernel implementations that include the unchecked xt_connmark module are affected. This includes the standard kernel used by most distributions as well as custom or embedded kernels that have not applied the recent patch. Any system that permits creation or modification of netfilter rules via xt_connmark without proper version checks is at risk; the vulnerability is not limited to a particular vendor, version, or kernel configuration.

The CVSS score of 7.3 indicates high severity; EPSS < 1% suggests a low exploitation probability. Based on the description, it is inferred that privileged users must add a malformed xt_connmark rule, so casual attackers cannot exploit it over the network. No public exploit exists and the need for elevated rights reduce the immediate threat level, yet the possibility of a system outage if the vulnerability is triggered remains significant. The CVE is not listed in CISA KEV, indicating no known widespread use of the flaw.