CVE-2026-68138 (GCVE-0-2026-68138)
Vulnerability from cvelistv5
Published
2026-08-10 11:59
Modified
2026-10-19 20:58
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: net/sched: serialize qdisc_rtab_list against concurrent get/put qdisc_get_rtab() and qdisc_put_rtab() mutate the process-global singly linked list qdisc_rtab_list and a plain non-atomic 'int refcnt' with no lock. This was only safe because every caller historically held the RTNL mutex, which serialized all rate-table lookups, inserts and frees. That invariant no longer holds. cls_flower sets TCF_PROTO_OPS_DOIT_UNLOCKED, so tc_new_tfilter() keeps rtnl_held == false for it and sets TCA_ACT_FLAGS_NO_RTNL. That flag propagates through tcf_exts_validate_ex() -> tcf_action_init() -> tcf_action_init_1() -> tcf_police_init(), which calls qdisc_get_rtab()/qdisc_put_rtab() with the RTNL mutex NOT held. Two RTM_NEWTFILTER requests on different CPUs, each adding a flower filter with a police action carrying the same rate, then race on qdisc_rtab_list and on the non-atomic refcnt, leading to a use-after-free / double-free of the kmalloc-2k struct qdisc_rate_table. qdisc_rtab_list is a single global (not per-netns), so the corrupted object is shared system-wide. BUG: KASAN: slab-use-after-free in qdisc_put_rtab+0x12f/0x160 qdisc_put_rtab+0x12f/0x160 tcf_police_init+0xda9/0x1590 tcf_action_init_1+0x460/0x6b0 tcf_action_init+0x439/0xa40 tcf_exts_validate_ex+0x42d/0x550 fl_change+0xddd/0x7da0 tc_new_tfilter+0xaa7/0x2420 rtnetlink_rcv_msg+0x95e/0xe90 which belongs to the cache kmalloc-2k of size 2048 Protect qdisc_rtab_list and the refcount with a dedicated spinlock. The (sleeping, GFP_KERNEL) allocation in qdisc_get_rtab() is performed before taking the lock; if a concurrent inserter added an identical table in the meantime the freshly allocated one is freed under the lock, so no duplicate is leaked. qdisc_put_rtab() now decrements the refcount and unlinks under the same lock.
References
Impacted products
Vendor Product Version
Linux Linux Version: 470502de5bdb1ed0def643a4458593a40b8f6b66
Version: 470502de5bdb1ed0def643a4458593a40b8f6b66
Version: 470502de5bdb1ed0def643a4458593a40b8f6b66
Version: 470502de5bdb1ed0def643a4458593a40b8f6b66
Version: 470502de5bdb1ed0def643a4458593a40b8f6b66
Version: 470502de5bdb1ed0def643a4458593a40b8f6b66
Version: 470502de5bdb1ed0def643a4458593a40b8f6b66
Version: 470502de5bdb1ed0def643a4458593a40b8f6b66
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          "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 \u0027int refcnt\u0027 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() -\u003e tcf_action_init() -\u003e tcf_action_init_1() -\u003e\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."
        }
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
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            {
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              "value": "AV:L - The bug is reached only via local RTM_NEWTFILTER rtnetlink messages (tc flower filter with police action) through rtnetlink_rcv_msg\u2192tc_new_tfilter\u2192fl_change\u2192tcf_police_init\u2192qdisc_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."
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        "dateUpdated": "2026-08-23T12:45:55.796Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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      "references": [
        {
          "url": "https://git.kernel.org/stable/c/1b050d09dd1a0ddae83bf012cf4956b7a960235f"
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        {
          "url": "https://git.kernel.org/stable/c/6e0241f6cbb149d926ee8efee2c734fea71452cf"
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        {
          "url": "https://git.kernel.org/stable/c/f93c89392bd3b180b5b7abc6fdae8e3dd667a313"
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        {
          "url": "https://git.kernel.org/stable/c/4131dd0b6f67acddd616ed7c244e1d3eedd46e7b"
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        },
        {
          "url": "https://git.kernel.org/stable/c/f43ee0c0730d6191629b5ee1ceae27b1ebfdc047"
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      "title": "net/sched: serialize qdisc_rtab_list against concurrent get/put",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-68138",
    "datePublished": "2026-08-10T11:59:01.744Z",
    "dateReserved": "2026-07-30T09:28:09.370Z",
    "dateUpdated": "2026-10-19T20:58:52.975Z",
    "state": "PUBLISHED"
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      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-68138\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"total\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-10-16T15:44:32.003419Z\"}}}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-362\", \"description\": \"CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization (\u0027Race Condition\u0027)\"}]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-10-16T15:44:32.799Z\"}}], \"cna\": {\"title\": \"net/sched: serialize qdisc_rtab_list against concurrent get/put\", \"metrics\": [{\"cvssV3_1\": {\"version\": \"3.1\", \"baseScore\": 7.8, \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\"}, \"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\\u2192tc_new_tfilter\\u2192fl_change\\u2192tcf_police_init\\u2192qdisc_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\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"470502de5bdb1ed0def643a4458593a40b8f6b66\", \"lessThan\": \"1b050d09dd1a0ddae83bf012cf4956b7a960235f\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"470502de5bdb1ed0def643a4458593a40b8f6b66\", \"lessThan\": \"6e0241f6cbb149d926ee8efee2c734fea71452cf\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"470502de5bdb1ed0def643a4458593a40b8f6b66\", \"lessThan\": \"f93c89392bd3b180b5b7abc6fdae8e3dd667a313\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"470502de5bdb1ed0def643a4458593a40b8f6b66\", \"lessThan\": \"4131dd0b6f67acddd616ed7c244e1d3eedd46e7b\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"470502de5bdb1ed0def643a4458593a40b8f6b66\", \"lessThan\": \"d981098b76756ed71666a27518eeb69883657c43\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"470502de5bdb1ed0def643a4458593a40b8f6b66\", \"lessThan\": \"8ddc2eb0d2da9c83f54f1e5720525b461b8480c4\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"470502de5bdb1ed0def643a4458593a40b8f6b66\", \"lessThan\": \"fb29e1b41052488ee3f2d115d4a870497ebd7f7d\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"470502de5bdb1ed0def643a4458593a40b8f6b66\", \"lessThan\": \"f43ee0c0730d6191629b5ee1ceae27b1ebfdc047\", \"versionType\": \"git\"}], \"programFiles\": [\"net/sched/sch_api.c\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"5.1\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"5.1\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"5.10.266\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"5.15.217\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.15.*\"}, {\"status\": \"unaffected\", \"version\": \"6.1.184\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.1.*\"}, {\"status\": \"unaffected\", \"version\": \"6.6.153\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.6.*\"}, {\"status\": \"unaffected\", \"version\": \"6.12.105\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.12.*\"}, {\"status\": \"unaffected\", \"version\": \"6.18.46\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.18.*\"}, {\"status\": \"unaffected\", \"version\": \"7.1.6\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"7.1.*\"}, {\"status\": \"unaffected\", \"version\": \"7.2\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"net/sched/sch_api.c\"], \"defaultStatus\": \"affected\"}], \"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\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"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 \u0027int refcnt\u0027 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() -\u003e tcf_action_init() -\u003e tcf_action_init_1() -\u003e\\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.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.266\", \"versionStartIncluding\": \"5.1\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.217\", \"versionStartIncluding\": \"5.1\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.1.184\", \"versionStartIncluding\": \"5.1\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.6.153\", \"versionStartIncluding\": \"5.1\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.12.105\", \"versionStartIncluding\": \"5.1\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.18.46\", \"versionStartIncluding\": \"5.1\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"7.1.6\", \"versionStartIncluding\": \"5.1\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"7.2\", \"versionStartIncluding\": \"5.1\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-08-23T12:45:55.796Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-68138\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-10-19T20:58:52.975Z\", \"dateReserved\": \"2026-07-30T09:28:09.370Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2026-08-10T11:59:01.744Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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