CVE-2026-68296

A flaw was found in the Linux kernel's Generic Routing Encapsulation (GRE) tunnel implementation. An issue with how lockless transmission was handled for GRE tunnels with Sequence Number (SEQ) or Checksum (CSUM) features could lead to a deadlock. This deadlock occurs when the GRE transmit function re-enters the network stack, potentially causing the system to become unresponsive, resulting in a Denial of Service (DoS).

This issue affects GRE tunnels with SEQ/CSUM features. Removal of NETIF_F_LLTX handling broke lockless transmit for sequenced GRE tunnels. Systems using plain GRE without SEQ/CSUM are less affected.

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.