The Linux kernel bug in the IPVS sync protocol allows malformed or unexpected message flags to be processed by the backup server. This can cause the kernel to perform incorrect lookups or create connections that violate its internal invariants, potentially leading to crashes or inconsistent state. The flaw is related to CWE-1288, indicating improper handling of input and lack of proper validation of connection flags.

The issue affects the Linux kernel IPVS subsystem used for load balancing. Any distribution that employs IPVS in a master‑backup configuration is impacted, provided the backup server uses the sync protocol to receive connection state. Distributions built on older or unpatched kernels without IPVS support are not affected.

The EPSS score is <1% and the vulnerability is not listed in CISA KEV, implying that no widespread exploitation has been reported. Exploitation would require the attacker to inject crafted sync messages, which is inferred to necessitate either control of the master node or a position to intercept or generate sync traffic between master and backup. The CVSS score of 6.5 reflects a moderate severity focused on denial of service, with no code execution or data tampering. The likely attack vector is network based, although this is explicitly inferred because the description does not state the vector.