CVE-2026-64422

Technical Description

In the Linux kernel, the following vulnerability has been resolved:

net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes

Reject invalid `net.ipv4.tcp_reordering` values before they reach TCP

socket state. The sysctl is stored as an `int` but copied into the

`u32` `tp->reordering` field for new sockets, so negative writes wrap

to large values.

With `tcp_mtu_probing=2`, the wrapped value can overflow the

`tcp_mtu_probe()` size calculation and drive the MTU probing path into

an out-of-bounds read. Route `tcp_reordering` writes through

`proc_dointvec_minmax()` and require it to be at least 1. Also require

`tcp_max_reordering` to be at least 1 so the configured maximum cannot

become negative either.

When registering the table for a non-init network namespace, relocate

`extra2` pointers that refer into `init_net.ipv4` so the

`tcp_reordering` upper bound follows that namespace's

`tcp_max_reordering`.

Harden `tcp_mtu_probe()` itself by computing `size_needed` as `u64`.

This k

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References