CVE-2026-64422: In the Linux kernel, the following vulnerability has been resolved: net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes Reject invalid...

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.

Metrics

CVSS 3.1

7.1/10

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

EPSS Probability

0.13%

3.1th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf, < f0d88a4cd03affff6c08adf6c63964e235aede43; >= 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf, < 27ddf4486c7dbf5bdd393fa8bef6b67179796d98; >= 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf, < 782708ca1ea1f68b8cbb5ea3a7f5f18d0000efae; >= 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf, < e81f805824a8109504fce090641b17d135b48cd1; >= 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf, < 99206ce2244f8a3ed64298d0667c9055845a5dc7; >= 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf, < bbae351c0f32f7c200249e4aa6561b2b419dcf69; >= 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf, < a094ac95d3b69adfa1676eb9c8eae6835d4f1671; >= 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf, < efb8763d7bbb40cff4cc55a6b62c3095a038149c
Linux	Linux	2.6.24

References

Timeline

Published: Jul 25, 2026
Last Modified: Aug 11, 2026
Status: Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-64422?

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.

How severe is CVE-2026-64422?

CVE-2026-64422 has a CVSS score of 7.1/10 (HIGH severity). The EPSS model estimates a 0.13% probability of exploitation in the next 30 days.

How do I fix CVE-2026-64422?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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