Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-07-25T00:00:00 kernel: net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes 7.0 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

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 keeps the send queue and window checks from being bypassed through signed integer overflow.

A flaw was found in the Linux kernel's IPv4 networking stack. Invalid values for `net.ipv4.tcp_reordering`, particularly negative inputs, can lead to an integer overflow when processed. When `tcp_mtu_probing` is enabled, this overflow can cause an out-of-bounds read within the `tcp_mtu_probe()` function. This vulnerability may allow an attacker to access sensitive information or cause system instability.

Red Hat Enterprise Linux 10 Affected kernel Red Hat Enterprise Linux 6 Out of support scope kernel Red Hat Enterprise Linux 7 Affected kernel Red Hat Enterprise Linux 7 Affected kernel-rt Red Hat Enterprise Linux 8 Affected kernel Red Hat Enterprise Linux 8 Affected kernel-rt Red Hat Enterprise Linux 9 Affected kernel Red Hat Enterprise Linux 9 Affected kernel-rt https://www.cve.org/CVERecord?id=CVE-2026-64422 https://nvd.nist.gov/vuln/detail/CVE-2026-64422 https://lore.kernel.org/linux-cve-announce/2026072534-CVE-2026-64422-d391@gregkh/T