{"id":"CVE-2026-98021","summary":"net: reject oversized tx_queue_len at netlink parse time","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: reject oversized tx_queue_len at netlink parse time\n\nrtnl_create_link() assigns IFLA_TXQLEN directly to dev-\u003etx_queue_len\nwithout going through netif_change_tx_queue_len(), so a device created\nwith \"ip link add ... txqueuelen 500000\" bypasses the S16_MAX cap and\nstill triggers the oversized ring allocations in pfifo_fast, tun and\ntap. The veth peer nest (rtnl_nla_parse_ifinfomsg()) and the\nRTM_NEWLINK-on-existing-device path reach the same sinks.\n\nEnforce the cap in ifla_policy instead: IFLA_TXQLEN becomes\nNLA_POLICY_FULL_RANGE(NLA_U32, &txqlen_range) with\ntxqlen_range = { .min = 0, .max = S16_MAX }. All netlink consumers\nparse against this policy - rtnl_setlink(), rtnl_newlink() (create\nand change), and the veth peer nest - so every netlink path is capped\nat parse time and rejects the attribute with -ERANGE plus a proper\n\"integer out of range\" extack message before any device state is\nmodified (the RTM_SETLINK half-application wart is gone with it).\n\nDocument the bound in the rt-link.yaml netlink spec.\n\nConditions to recreate the bug:\n- CONFIG_NET_SCHED=y, CONFIG_VETH=y, CONFIG_USER_NS=y, CONFIG_NET_NS=y.\n- Unprivileged user in a fresh user+net namespace (unshare -Urn):\n  ip link add v0 txqueuelen 500000 type veth peer name v1\n  -\u003e on the fixed kernel this is rejected with -ERANGE (\"integer out\n  of range\" extack) instead of installing an oversized tx_queue_len\n  that later inflates pfifo_fast/tun/tap ring allocations.\n- ip link set v0 txqueuelen 500000 is likewise rejected at parse time.","modified":"2026-09-26T03:48:36.997340091Z","published":"2026-09-25T10:23:41.505Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98021.json"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/1aa9e143bf51405665a793d4cc925e1c4f0c5922"},{"type":"WEB","url":"https://git.kernel.org/stable/c/2fd0880f0272ec022906a05587fd91416ebecc38"},{"type":"WEB","url":"https://git.kernel.org/stable/c/45ca9f59b6c7ea70e0a17054902b8a556913db34"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a638a2625aa83160a394abe8e8b2e524a80c771b"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98021.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98021"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"38f7b870d4a6a5d3ec21557e849620cb7d032965"},{"fixed":"45ca9f59b6c7ea70e0a17054902b8a556913db34"},{"fixed":"2fd0880f0272ec022906a05587fd91416ebecc38"},{"fixed":"a638a2625aa83160a394abe8e8b2e524a80c771b"},{"fixed":"1aa9e143bf51405665a793d4cc925e1c4f0c5922"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98021.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.6.23"},{"fixed":"6.12.111"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.53"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.7"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98021.json"}}],"schema_version":"1.9.0"}