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.
CSIRTS triage
- What
- There is a vulnerability related to TCP reordering sysctl writes and MTU probe sizes.
- Who is affected
- Deployments of the Linux kernel that utilize TCP settings.
- Urgency
- Remediation is important to ensure network stability, with no known exploits currently.
- Action
- Update to the latest kernel version that includes the fix.
AI-assisted analysis generated from the source advisory — verify against the original.
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Exploitation outlook
- Low exploitation risk0.13% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 3% of all EPSS-scored CVEs.
Advisory coverage (2)
External references
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