{"id":"CVE-2026-98598","title":"ipv6: Prevent rt6_insert_exception() for dying fib6_info.","summary":"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_e…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= cc5c073a693fa6ed7a207b0436114f68cce72434 < 649ffc76ed5483b2caf35ed90d3787538efc4e53","Linux >= cc5c073a693fa6ed7a207b0436114f68cce72434 < e03e77071e75ce726d877f0a4349a28b6e1f487a","Linux >= cc5c073a693fa6ed7a207b0436114f68cce72434 < 0346ec2f080b40d95ed05b853bb9226289e75212","Linux 5.3"],"published":"2026-10-18","updated":"2026-10-18","sourceUpdated":"2026-10-18T15:19:11.126Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98598","references":[{"url":"https://git.kernel.org/stable/c/649ffc76ed5483b2caf35ed90d3787538efc4e53"},{"url":"https://git.kernel.org/stable/c/e03e77071e75ce726d877f0a4349a28b6e1f487a"},{"url":"https://git.kernel.org/stable/c/0346ec2f080b40d95ed05b853bb9226289e75212"}],"tags":["cve.org"],"ingestedAt":"2026-10-18T15:45:12.245Z","slug":"CVE-2026-98598","body":"## Overview\n\nIn 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.\n\n## Affected\n\n- `Linux >= cc5c073a693fa6ed7a207b0436114f68cce72434 < 649ffc76ed5483b2caf35ed90d3787538efc4e53`\n- `Linux >= cc5c073a693fa6ed7a207b0436114f68cce72434 < e03e77071e75ce726d877f0a4349a28b6e1f487a`\n- `Linux >= cc5c073a693fa6ed7a207b0436114f68cce72434 < 0346ec2f080b40d95ed05b853bb9226289e75212`\n- `Linux 5.3`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}