CVE-2026-43198 tcp: fix potential race in tcp_v6_syn_recv_sock()

What is CVE-2026-43198?

CVE-2026-43198 is a critical vulnerability in Linux kernel, published on 6 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

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.

Weakness: CWE-821, CWE-362

Which versions are affected by CVE-2026-43198?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-43198?

Apply the vendor's patch.

Is CVE-2026-43198 being exploited?

There is no known exploitation of CVE-2026-43198 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-85803, BELL-CVE-2026-43198, DEBIAN-CVE-2026-43198, GHSA-rhcj-6wxj-r34p, ROOT-OS-DEBIAN-11-CVE-2026-43198, ROOT-OS-DEBIAN-12-CVE-2026-43198 and 4 more.