{"id":"CVE-2026-98598","state":"PUBLISHED","title":"ipv6: Prevent rt6_insert_exception() for dying fib6_info.","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.","publishedAt":"2026-10-18T15:19:11.126Z","updatedAt":"2026-10-19T09:22:24.055Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"cc5c073a693fa6ed7a207b0436114f68cce72434","status":"affected","lessThan":"649ffc76ed5483b2caf35ed90d3787538efc4e53","versionType":"git"},{"version":"cc5c073a693fa6ed7a207b0436114f68cce72434","status":"affected","lessThan":"e03e77071e75ce726d877f0a4349a28b6e1f487a","versionType":"git"},{"version":"cc5c073a693fa6ed7a207b0436114f68cce72434","status":"affected","lessThan":"0346ec2f080b40d95ed05b853bb9226289e75212","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/ip6_fib.c","net/ipv6/route.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.3","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.3","versionType":"semver"},{"version":"6.18.55","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.9","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/ip6_fib.c","net/ipv6/route.c"]}],"references":["https://git.kernel.org/stable/c/649ffc76ed5483b2caf35ed90d3787538efc4e53","https://git.kernel.org/stable/c/e03e77071e75ce726d877f0a4349a28b6e1f487a","https://git.kernel.org/stable/c/0346ec2f080b40d95ed05b853bb9226289e75212"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98598.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98598","state":"PUBLISHED","datePublished":"2026-10-18T15:19:11.126Z","dateUpdated":"2026-10-19T09:22:24.055Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.359Z"},"containers":{"cna":{"title":"ipv6: Prevent rt6_insert_exception() for dying fib6_info.","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"cc5c073a693fa6ed7a207b0436114f68cce72434","status":"affected","lessThan":"649ffc76ed5483b2caf35ed90d3787538efc4e53","versionType":"git"},{"version":"cc5c073a693fa6ed7a207b0436114f68cce72434","status":"affected","lessThan":"e03e77071e75ce726d877f0a4349a28b6e1f487a","versionType":"git"},{"version":"cc5c073a693fa6ed7a207b0436114f68cce72434","status":"affected","lessThan":"0346ec2f080b40d95ed05b853bb9226289e75212","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/ip6_fib.c","net/ipv6/route.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.3","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.3","versionType":"semver"},{"version":"6.18.55","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.9","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/ip6_fib.c","net/ipv6/route.c"]}],"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"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T09:22:24.055Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"6.18.55"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"7.2.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}