{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-68138","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-07-30T09:28:09.370Z","datePublished":"2026-08-10T11:59:01.744Z","dateUpdated":"2026-08-23T12:45:55.796Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-23T12:45:55.796Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: serialize qdisc_rtab_list against concurrent get/put\n\nqdisc_get_rtab() and qdisc_put_rtab() mutate the process-global singly\nlinked list qdisc_rtab_list and a plain non-atomic 'int refcnt' with no\nlock. This was only safe because every caller historically held the RTNL\nmutex, which serialized all rate-table lookups, inserts and frees.\n\nThat invariant no longer holds. cls_flower sets\nTCF_PROTO_OPS_DOIT_UNLOCKED, so tc_new_tfilter() keeps rtnl_held == false\nfor it and sets TCA_ACT_FLAGS_NO_RTNL. That flag propagates through\ntcf_exts_validate_ex() -> tcf_action_init() -> tcf_action_init_1() ->\ntcf_police_init(), which calls qdisc_get_rtab()/qdisc_put_rtab() with the\nRTNL mutex NOT held. Two RTM_NEWTFILTER requests on different CPUs, each\nadding a flower filter with a police action carrying the same rate, then\nrace on qdisc_rtab_list and on the non-atomic refcnt, leading to a\nuse-after-free / double-free of the kmalloc-2k struct qdisc_rate_table.\nqdisc_rtab_list is a single global (not per-netns), so the corrupted\nobject is shared system-wide.\n\n  BUG: KASAN: slab-use-after-free in qdisc_put_rtab+0x12f/0x160\n   qdisc_put_rtab+0x12f/0x160\n   tcf_police_init+0xda9/0x1590\n   tcf_action_init_1+0x460/0x6b0\n   tcf_action_init+0x439/0xa40\n   tcf_exts_validate_ex+0x42d/0x550\n   fl_change+0xddd/0x7da0\n   tc_new_tfilter+0xaa7/0x2420\n   rtnetlink_rcv_msg+0x95e/0xe90\n  which belongs to the cache kmalloc-2k of size 2048\n\nProtect qdisc_rtab_list and the refcount with a dedicated spinlock. The\n(sleeping, GFP_KERNEL) allocation in qdisc_get_rtab() is performed before\ntaking the lock; if a concurrent inserter added an identical table in the\nmeantime the freshly allocated one is freed under the lock, so no\nduplicate is leaked. qdisc_put_rtab() now decrements the refcount and\nunlinks under the same lock."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bug is reached only via local RTM_NEWTFILTER rtnetlink messages (tc flower filter with police action) through rtnetlink_rcv_msg→tc_new_tfilter→fl_change→tcf_police_init→qdisc_get_rtab/qdisc_put_rtab; no remote packet or network protocol path exists.\nAC:L - cls_flower is TCF_PROTO_OPS_DOIT_UNLOCKED, so concurrent RTM_NEWTFILTER requests run without RTNL; the attacker controls both racing threads/CPUs and can repeatedly install flower filters with identical police rate tables to deterministically hit the global qdisc_rtab_list/refcnt race.\nPR:L - Non-GET rtnetlink handlers require netlink_net_capable(CAP_NET_ADMIN); this is namespace-scoped, so an unprivileged local user obtains CAP_NET_ADMIN via user namespaces (unshare -Urn), sets up clsact/ingress, and installs flower+police rules without init-namespace root.\nUI:N - Exploitation is fully self-contained: the attacker issues the concurrent tc/netlink commands from its own processes and needs no victim to mount filesystems, click links, or perform any other interactive action.\nS:U - Impact is heap corruption and UAF/double-free in kernel kmalloc-2k slabs within the same kernel security authority; although qdisc_rtab_list is global across netns, this is standard kernel memory corruption/privilege escalation, not a VM, IOMMU, or sandbox boundary escape.\nC:H - Concurrent non-atomic refcnt and list updates cause slab use-after-free/double-free of struct qdisc_rate_table (KASAN-confirmed in qdisc_put_rtab); freed 2KB objects are attacker-influenceable via kmalloc timing and are classically weaponizable for arbitrary kernel memory disclosure.\nI:H - The race corrupts a process-global singly linked list and can double-free a kmalloc-2k qdisc_rate_table, yielding classic heap metadata/object corruption primitives that can be developed into arbitrary kernel writes and local privilege escalation/code execution.\nA:H - Demonstrated KASAN slab-use-after-free in qdisc_put_rtab on the error/teardown path, and concurrent double-free of the same rate table can panic the kernel; the trigger is repeatable at will with concurrent netlink requests and causes task death or system-wide instability."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_api.c"],"versions":[{"version":"470502de5bdb1ed0def643a4458593a40b8f6b66","lessThan":"1b050d09dd1a0ddae83bf012cf4956b7a960235f","status":"affected","versionType":"git"},{"version":"470502de5bdb1ed0def643a4458593a40b8f6b66","lessThan":"6e0241f6cbb149d926ee8efee2c734fea71452cf","status":"affected","versionType":"git"},{"version":"470502de5bdb1ed0def643a4458593a40b8f6b66","lessThan":"f93c89392bd3b180b5b7abc6fdae8e3dd667a313","status":"affected","versionType":"git"},{"version":"470502de5bdb1ed0def643a4458593a40b8f6b66","lessThan":"4131dd0b6f67acddd616ed7c244e1d3eedd46e7b","status":"affected","versionType":"git"},{"version":"470502de5bdb1ed0def643a4458593a40b8f6b66","lessThan":"d981098b76756ed71666a27518eeb69883657c43","status":"affected","versionType":"git"},{"version":"470502de5bdb1ed0def643a4458593a40b8f6b66","lessThan":"8ddc2eb0d2da9c83f54f1e5720525b461b8480c4","status":"affected","versionType":"git"},{"version":"470502de5bdb1ed0def643a4458593a40b8f6b66","lessThan":"fb29e1b41052488ee3f2d115d4a870497ebd7f7d","status":"affected","versionType":"git"},{"version":"470502de5bdb1ed0def643a4458593a40b8f6b66","lessThan":"f43ee0c0730d6191629b5ee1ceae27b1ebfdc047","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sched/sch_api.c"],"versions":[{"version":"5.1","status":"affected"},{"version":"0","lessThan":"5.1","status":"unaffected","versionType":"semver"},{"version":"5.10.266","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.217","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.184","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.153","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.105","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.46","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.1.6","lessThanOrEqual":"7.1.*","status":"unaffected","versionType":"semver"},{"version":"7.2","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.1","versionEndExcluding":"5.10.266"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.1","versionEndExcluding":"5.15.217"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.1","versionEndExcluding":"6.1.184"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.1","versionEndExcluding":"6.6.153"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.1","versionEndExcluding":"6.12.105"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.1","versionEndExcluding":"6.18.46"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.1","versionEndExcluding":"7.1.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.1","versionEndExcluding":"7.2"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/1b050d09dd1a0ddae83bf012cf4956b7a960235f"},{"url":"https://git.kernel.org/stable/c/6e0241f6cbb149d926ee8efee2c734fea71452cf"},{"url":"https://git.kernel.org/stable/c/f93c89392bd3b180b5b7abc6fdae8e3dd667a313"},{"url":"https://git.kernel.org/stable/c/4131dd0b6f67acddd616ed7c244e1d3eedd46e7b"},{"url":"https://git.kernel.org/stable/c/d981098b76756ed71666a27518eeb69883657c43"},{"url":"https://git.kernel.org/stable/c/8ddc2eb0d2da9c83f54f1e5720525b461b8480c4"},{"url":"https://git.kernel.org/stable/c/fb29e1b41052488ee3f2d115d4a870497ebd7f7d"},{"url":"https://git.kernel.org/stable/c/f43ee0c0730d6191629b5ee1ceae27b1ebfdc047"}],"title":"net/sched: serialize qdisc_rtab_list against concurrent get/put","x_generator":{"engine":"bippy-1.2.0"}}}}