CVE-2026-23099: 
Linux Kernel vulnerability analysis and mitigation

CVE-2026-23099 is an out-of-bounds read vulnerability in the Linux kernel's bonding driver, caused by BOND_MODE_8023AD not being properly restricted to Ethernet (ARPHRD_ETHER) devices. When a non-Ethernet device is enslaved in 802.3ad mode, the kernel performs an out-of-bounds global memory read in net/core/dev_addr_lists.c during multicast address operations. The vulnerability was published on February 4, 2026, and affects Linux kernel versions from 2.6.24 up through multiple stable branches. It carries a CVSS v3.1 base score of 7.1 (High), requiring only local access with low privileges (Feedly).

The root cause is classified as CWE-125 (Out-of-bounds Read). The bonding driver's bond_enslave() function in drivers/net/bonding/bond_main.c calls dev_mc_add() to add multicast addresses when operating in BOND_MODE_8023AD, but does not validate that the enslaved device is of type ARPHRD_ETHER. When a non-Ethernet device is used, __hw_addr_create() in net/core/dev_addr_lists.c performs a 16-byte memory read at an address outside valid bounds, as detected by KASAN (global-out-of-bounds at ffffffff8bf94040). The attack vector is local, exploitable via rtnetlink/netlink socket operations by a low-privileged user to manipulate bonding interfaces (Feedly).

Successful exploitation can result in disclosure of sensitive kernel memory contents (confidentiality impact) and a system crash or kernel panic (availability impact), constituting a denial-of-service condition. There is no integrity impact. The vulnerability is confined to the local system and does not directly enable lateral movement, but kernel memory disclosure could potentially expose credentials or cryptographic material useful for further attacks (Feedly).

1. Gain local access: Obtain a low-privileged local shell on a vulnerable Linux system (kernel versions 2.6.24 through pre-patch stable releases).
2. Check bonding module: Verify the bonding kernel module is loaded (lsmod | grep bonding); load it if necessary (modprobe bonding).
3. Create a bond interface in 802.3ad mode: Use ip link add bond0 type bond mode 802.3ad or equivalent netlink/rtnetlink commands to create a bonding interface configured for BOND_MODE_8023AD.
4. Identify a non-Ethernet interface: Select a non-Ethernet network device (e.g., a loopback or tunnel interface not of type ARPHRD_ETHER) present on the system.
5. Enslave the non-Ethernet device: Issue ip link set <non-eth-dev> master bond0 via rtnetlink, triggering bond_enslave() which calls dev_mc_add() without device-type validation.
6. Trigger out-of-bounds read: The kernel executes __hw_addr_create() with an invalid address length for the non-Ethernet device, causing a global out-of-bounds read — resulting in kernel memory disclosure or a kernel panic/crash (Feedly).

• Logs: Kernel logs (dmesg / /var/log/kern.log) showing KASAN reports: BUG: KASAN: global-out-of-bounds in __hw_addr_create or __hw_addr_add_ex in net/core/dev_addr_lists.c; kernel oops or panic traces referencing bond_enslave and dev_mc_add.
• Process: Unusual processes invoking ip link set <device> master <bond> with non-Ethernet devices, or netlink socket activity from unexpected low-privileged users configuring bonding interfaces.
• Network: Unexpected bonding interface (bond*) creation events visible via ip link show or audit logs, particularly with non-Ethernet slave devices attached.

Upgrade to a patched Linux kernel version: 5.15.199 or later (5.15.x series), 6.1.162 or later (6.1.x series), 6.6.122 or later (6.6.x series), 6.12.68 or later (6.12.x series), or 6.18.8 or later (6.18.x series). Patches are available via kernel.org stable branches. As interim workarounds: restrict local user access to netlink socket operations (e.g., via CAP_NET_ADMIN capability restrictions or seccomp policies), disable the bonding driver (rmmod bonding / blacklist in /etc/modprobe.d/) if not operationally required, and apply vendor-specific kernel updates from distributions such as Ubuntu (USN-8162-1, USN-8180-x, USN-8186-1, USN-8188-1, USN-8275-1, USN-8297-1), SUSE, Oracle Linux, and Amazon Linux 2 (Feedly, Ubuntu Advisory).

The vulnerability was reported by syzbot (Google's automated kernel fuzzing infrastructure), which identified the KASAN global-out-of-bounds crash during bond enslaving operations. Multiple Linux distributions — including Ubuntu, SUSE, Oracle Linux, and Amazon Linux 2 — have issued kernel security advisories addressing this CVE. The SANS Internet Storm Center published a diary entry referencing this vulnerability. No notable individual researcher commentary or significant social media discussion has been identified beyond standard distribution advisory channels (Feedly, SANS ISC).