CVE-2021-47222

A flaw was found in the Linux kernel's bridge subsystem. When processing Virtual Local Area Network (VLAN) egress tunnels, the bridge code improperly clones destination cache entries that may already be deleted or have an expired reference count. A local user could exploit this flaw to cause reference count underflows and kernel warnings, leading to a system crash and Denial of Service (DoS).

Red Hat has evaluated this issue as having a Low severity impact because exploiting it requires an uncommonly configured bridge environment and only results in a local denial of service without compromising system confidentiality or integrity. Standard Red Hat Enterprise Linux deployments do not configure bridge VLAN tunnel egress mapping by default, which restricts exposure to specialized network topologies. Triggering the flaw requires specific administrative privileges or existing egress tunnel interfaces, limiting the blast radius to a kernel warning or system crash.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.