SEPTEMBER 20, 2026
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Case File

CVE-2026-64422

HIGH · CVSS 7.1 EPSS 0.13%

Source: NVD + CISA KEV + EPSS · Published 2026-07-25 · Last synced 2026-08-24

CyberRota Analysis

AI-Generated

The vulnerability affects the Linux kernel's handling of TCP reordering parameters, specifically allowing invalid values for `net.ipv4.tcp_reordering` to be written, which can lead to out-of-bounds reads during MTU probing. This flaw could potentially be exploited to cause denial-of-service conditions or unexpected behavior in network communications. Organizations using Linux systems, particularly those managing network services, should prioritize addressing this vulnerability to mitigate risks associated with network stability and security.

CVE
CVE-2026-64422
Severity
HIGH
CVSS
7.1
EPSS
0.13%
Linux

Original NVD 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.