{"id":"CVE-2026-98598","published":"2026-10-18T16:17:12.500","lastModified":"2026-10-19T10:19:21.240","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: Prevent rt6_insert_exception() for dying fib6_info.\n\nBefore the cited commit, fib6_nh_flush_exceptions() always set\nfrom->exception_bucket_flushed = 1 under rt6_exception_lock to\nprevent rt6_insert_exception() from inserting a new exception\nfor a dying fib6_info.\n\nThe flag was replaced with the FIB6_EXCEPTION_BUCKET_FLUSHED\nbit stored in nh->rt6i_exception_bucket.\n\nThe problem is that now the bit is only set when the bucket\nis not NULL and fib6_nh_flush_exceptions() is called from\nfib6_nh_release() after fib6_ref has already reached zero.\n\nIf rt6_insert_exception() is called while the target fib6_info\nis being removed via fib6_purge_rt(), a new exception could be\ncreated successfully because rt6_flush_exceptions() no longer\nsets the bit.\n\nThis creates a reference cycle between the fib6_info and the\nexception route, leaking the fib6_info, its nexthop device,\nand all per-CPU routes in fib6_nh->rt6i_pcpu, which stalls netdev\nunregistration.\n\n[   34.680602] unregister_netdevice: waiting for gre6 to become free. Usage count = 68\n[   44.920675] unregister_netdevice: waiting for gre6 to become free. Usage count = 68\n[   55.176582] unregister_netdevice: waiting for gre6 to become free. Usage count = 68\n\nLet's call fib6_drop_pcpu_from() before rt6_flush_exceptions(),\nto set fib6_destroying before rt6_exception_lock, and check\nf6i->fib6_destroying in rt6_insert_exception().\n\nNote that FIB6_EXCEPTION_BUCKET_FLUSHED logic is dead and\nwe can clean it up in net-next.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/0346ec2f080b40d95ed05b853bb9226289e75212","tags":[]},{"url":"https://git.kernel.org/stable/c/649ffc76ed5483b2caf35ed90d3787538efc4e53","tags":[]},{"url":"https://git.kernel.org/stable/c/e03e77071e75ce726d877f0a4349a28b6e1f487a","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}