CVE-2026-63925

A flaw was found in the Linux kernel's MACsec (Media Access Control Security) subsystem. When using Extended Packet Numbering (XPN), a vulnerability exists where the replay protection mechanism can be bypassed. An attacker can exploit an integer overflow when the packet number reaches its maximum value, allowing them to indefinitely replay legitimate MACsec frames. This can lead to a disruption of secure communication and unauthorized re-transmission of data.

This vulnerability is rated as Moderate because successful exploitation requires access to the adjacent network link and an active MACsec interface configured specifically with Extended Packet Numbering (XPN), limiting the attack surface to specialized network deployments. MACsec is not active by default in Red Hat Enterprise Linux and requires explicit administrative setup. Furthermore, triggering the condition requires an attacker to monitor traffic until the lower 32-bit packet sequence wraps, allowing replay of captured frames without granting broader privilege escalation or system compromise.

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.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.