CVE-2026-43339 is a use-after-free vulnerability in the Linux kernel's IPv6 address configuration function addrconf_permanent_addr(). The issue arises because a warning message is delivered too late, causing access to IPv6 data after it may have been deleted. The vulnerability has been addressed by reordering the code to avoid the use-after-free and moving the warning outside the lock protection. This flaw has a high severity rating with a CVSS score of 7.8.