Out-of-bounds write in Linux kernel - CVE-2026-98570

Vulnerability identifier: #VU156873

CSH Severity: Medium

CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-98570

CWE-ID: CWE-787

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to cause a denial of service by triggering kernel memory corruption.

The vulnerability exists due to insufficient MAC-header headroom allocation in dst_dev_overhead() when IPv6 lightweight tunnels rebuild headers for packets whose MAC header exceeds the egress device's reserved space. A remote attacker can send IPv6 traffic through an affected forwarding path to trigger an out-of-bounds write in kernel memory and potentially crash the system.

An affected ingress configuration is a VLAN device with reorder_hdr disabled.

Linux kernel
Ubuntu
linux (Ubuntu package)
linux-aws (Ubuntu package)
linux-gcp (Ubuntu package)
linux-oracle (Ubuntu package)
linux-ibm (Ubuntu package)
linux-hwe-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux (Ubuntu package) - update to 7.0.0-42.42
linux-aws (Ubuntu package) - update to 7.0.0-1016.17
linux-gcp (Ubuntu package) - update to 7.0.0-1016.18
linux-oracle (Ubuntu package) - update to 7.0.0-1015.16
linux-ibm (Ubuntu package) - update to 7.0.0-1017.17
linux-hwe-7.0 (Ubuntu package) - update to 7.0.0-42.42~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1017.17

• https://git.kernel.org/stable/c/36c07127924f11fc5741a780abcaaf808fe9ef13
• https://git.kernel.org/stable/c/87cd6b717e4069dca34e0866e57eaeb44d3b173e

• Out-of-bounds write in Linux kernel net
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux, linux-aws, linux-gcp and more