CVE-2026-64422net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes

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

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/f0d88a4cd03affff6c08adf6c63964e235aede43
• https://git.kernel.org/stable/c/27ddf4486c7dbf5bdd393fa8bef6b67179796d98
• https://git.kernel.org/stable/c/782708ca1ea1f68b8cbb5ea3a7f5f18d0000efae
• https://git.kernel.org/stable/c/e81f805824a8109504fce090641b17d135b48cd1
• https://git.kernel.org/stable/c/99206ce2244f8a3ed64298d0667c9055845a5dc7
• https://git.kernel.org/stable/c/bbae351c0f32f7c200249e4aa6561b2b419dcf69
• https://git.kernel.org/stable/c/a094ac95d3b69adfa1676eb9c8eae6835d4f1671
• https://git.kernel.org/stable/c/efb8763d7bbb40cff4cc55a6b62c3095a038149c
• https://cert-portal.siemens.com/productcert/html/ssa-019113.html
• https://cert-portal.siemens.com/productcert/html/ssa-457936.html