CVE-2026-89562

A flaw was found in the Linux kernel's IPv6 Generic Routing Encapsulation (GRE) subsystem. The kernel incorrectly calculates the hardware header length for Non-Broadcast Multiple Access (NBMA) tunnel interfaces by improperly accumulating the underlying device's header length. A local authenticated attacker could exploit this flaw to trigger improper packet buffer handling, potentially leading to a Denial of Service (DoS) via a system crash.

This vulnerability is rated with a Low severity impact because exploiting it requires local authenticated access and relies on specific Non-Broadcast Multiple Access (NBMA) IPv6 GRE configurations that are not enabled by default in Red Hat Enterprise Linux. Default enterprise installations do not configure NBMA tunnel interfaces, substantially restricting exposure under standard operating conditions. Even if an administrator configures the relevant tunnel endpoints, successful exploitation is limited to causing a denial of service through kernel crash or panic, without threatening host confidentiality or data integrity.

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.