UBUNTU-CVE-2026-43198
In the Linux kernel, the following vulnerability has been resolved: tcp: fix potential race in tcp_v6_syn_recv_sock() Code in tcp_v6_syn_recv_sock() after the call to tcp_v4_syn_recv_sock() is done too late. After tcp_v4_syn_recv_sock(), the child socket is already visible from TCP ehash table and other cpus might use it. Since newinet->pinet6 is still pointing to the listener ipv6_pinfo bad things can happen as syzbot found. Move the problematic code in tcp_v6_mapped_child_init() and call this new helper from tcp_v4_syn_recv_sock() before the ehash insertion. This allows the removal of one tcp_sync_mss(), since tcp_v4_syn_recv_sock() will call it with the correct context.
02 / AFFECTED SOFTWARE
Affected packages
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03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: tcp: fix potential race in tcp_v6_syn_recv_sock() Code in tcp_v6_syn_recv_sock() after the call to tcp_v4_syn_recv_sock() is done too late. After tcp_v4_syn_recv_sock(), the child socket is already visible from TCP ehash table and other cpus might use it. Since newinet->pinet6 is still pointing to the listener ipv6_pinfo bad things can happen as syzbot found. Move the problematic code in tcp_v6_mapped_child_init() and call this new helper from tcp_v4_syn_recv_sock() before the ehash insertion. This allows the removal of one tcp_sync_mss(), since tcp_v4_syn_recv_sock() will call it with the correct context.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/858d2a4f67ff69e645a43487ef7ea7f28f06deae
- https://ubuntu.com/security/CVE-2026-43198
- https://ubuntu.com/security/notices/USN-8630-1
- https://ubuntu.com/security/notices/USN-8630-2
- https://ubuntu.com/security/notices/USN-8630-3
- https://ubuntu.com/security/notices/USN-8631-1
- https://ubuntu.com/security/notices/USN-8631-2
- https://ubuntu.com/security/notices/USN-8631-3
- https://ubuntu.com/security/notices/USN-8631-4
- https://ubuntu.com/security/notices/USN-8633-1
- https://ubuntu.com/security/notices/USN-8633-2
- https://ubuntu.com/security/notices/USN-8634-1
- https://ubuntu.com/security/notices/USN-8635-1
- https://ubuntu.com/security/notices/USN-8636-1
- https://ubuntu.com/security/notices/USN-8636-2
- https://ubuntu.com/security/notices/USN-8645-1
- https://www.cve.org/CVERecord?id=CVE-2026-43198