{"id":"CVE-2026-45845","title":"net/sched: taprio: fix NULL pointer dereference in class dump","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: taprio: fix NULL pointer dereference in class dump\n\nWhen a TAPRIO child qdisc is deleted via RTM_DELQDISC, taprio_graft()\nis called with new == NULL and stor…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 < ec2501e361b08b50bcb1e7b3253fc861abbda28d","Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 < d02e2fbf60de46678e2ea698a6a904fd21e1cc31","Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 < 48b26d48e76221dc90b02bf5428bab53643461ca","Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 < 8f1ff8866cb9f655e5faea6994eb902960be8e04","Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 < 3d07ca5c0fae311226f737963984bd94bb159a87","Linux 6.6"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-11-06T15:41:59.608192Z"},"published":"2026-05-27","updated":"2026-11-06","sourceUpdated":"2026-11-06T15:42:59.407Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-45845","references":[{"url":"https://git.kernel.org/stable/c/ec2501e361b08b50bcb1e7b3253fc861abbda28d"},{"url":"https://git.kernel.org/stable/c/d02e2fbf60de46678e2ea698a6a904fd21e1cc31"},{"url":"https://git.kernel.org/stable/c/48b26d48e76221dc90b02bf5428bab53643461ca"},{"url":"https://git.kernel.org/stable/c/8f1ff8866cb9f655e5faea6994eb902960be8e04"},{"url":"https://git.kernel.org/stable/c/3d07ca5c0fae311226f737963984bd94bb159a87"}],"tags":["cve.org"],"epss":0.0012,"epssPercentile":0.01813,"ingestedAt":"2026-11-06T15:54:03.881Z","slug":"CVE-2026-45845","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: taprio: fix NULL pointer dereference in class dump\n\nWhen a TAPRIO child qdisc is deleted via RTM_DELQDISC, taprio_graft()\nis called with new == NULL and stores NULL into q->qdiscs[cl - 1].\nSubsequent RTM_GETTCLASS dump operations walk all classes via\ntaprio_walk() and call taprio_dump_class(), which calls taprio_leaf()\nreturning the NULL pointer, then dereferences it to read child->handle,\ncausing a kernel NULL pointer dereference.\n\nThe bug is reachable with namespace-scoped CAP_NET_ADMIN on any kernel\nwith CONFIG_NET_SCH_TAPRIO enabled. On systems with unprivileged user\nnamespaces enabled, an unprivileged local user can trigger a kernel\npanic by creating a taprio qdisc inside a new network namespace,\ngrafting an explicit child qdisc, deleting it, and requesting a class\ndump. The RTM_GETTCLASS dump itself requires no capability.\n\n Oops: general protection fault, probably for non-canonical address 0xdffffc0000000007: 0000 [#1] SMP KASAN NOPTI\n KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]\n RIP: 0010:taprio_dump_class (net/sched/sch_taprio.c:2478)\n Call Trace:\n  <TASK>\n  tc_fill_tclass (net/sched/sch_api.c:1966)\n  qdisc_class_dump (net/sched/sch_api.c:2326)\n  taprio_walk (net/sched/sch_taprio.c:2514)\n  tc_dump_tclass_qdisc (net/sched/sch_api.c:2352)\n  tc_dump_tclass_root (net/sched/sch_api.c:2370)\n  tc_dump_tclass (net/sched/sch_api.c:2431)\n  rtnl_dumpit (net/core/rtnetlink.c:6864)\n  netlink_dump (net/netlink/af_netlink.c:2325)\n  rtnetlink_rcv_msg (net/core/rtnetlink.c:6959)\n  netlink_rcv_skb (net/netlink/af_netlink.c:2550)\n  </TASK>\n\nFix this by substituting &noop_qdisc when new is NULL in\ntaprio_graft(), a common pattern used by other qdiscs (e.g.,\nmultiq_graft()) to ensure the q->qdiscs[] slots are never NULL.\nThis makes control-plane dump paths safe without requiring individual\nNULL checks.\n\nSince the data-plane paths (taprio_enqueue and taprio_dequeue_from_txq)\npreviously had explicit NULL guards that would drop/skip the packet\ncleanly, update those checks to test for &noop_qdisc instead. Without\nthis, packets would reach taprio_enqueue_one() which increments the root\nqdisc's qlen and backlog before calling the child's enqueue; noop_qdisc\ndrops the packet but those counters are never rolled back, permanently\ninflating the root qdisc's statistics.\n\nAfter this change *old can be a valid qdisc, NULL, or &noop_qdisc.\nOnly call qdisc_put(*old) in the first case to avoid decreasing\nnoop_qdisc's refcount, which was never increased.\n\n## Affected\n\n- `Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 < ec2501e361b08b50bcb1e7b3253fc861abbda28d`\n- `Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 < d02e2fbf60de46678e2ea698a6a904fd21e1cc31`\n- `Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 < 48b26d48e76221dc90b02bf5428bab53643461ca`\n- `Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 < 8f1ff8866cb9f655e5faea6994eb902960be8e04`\n- `Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 < 3d07ca5c0fae311226f737963984bd94bb159a87`\n- `Linux 6.6`\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":[]}