CVE-2026-64422
HighCVSS 7.1Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
In the Linux kernel, the TCP/IP stack has a vulnerability due to missing validation of the net.ipv4.tcp_reordering sysctl value. Negative values written to this sysctl are copied to the tp->reordering field as u32, causing wrap to large values. This can lead to overflow in MTU size calculations and out-of-bounds read. The fix adds validation via proc_dointvec_minmax() and secures calculations by using u64.
Risk Assessment
The organization may be exposed to out-of-bounds read attacks in the MTU probing path, potentially leading to information leaks or system instability.
Recommendation
It is recommended to update the Linux kernel to a version containing the fix for CVE-2026-64422 to prevent potential attacks on the TCP/IP stack.
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Original NVD description (English source)
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.