{"id":"CVE-2026-68138","title":"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 …","summary":"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 …","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","published":"2026-08-10","updated":"2026-08-23","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-68138","references":[{"url":"https://git.kernel.org/stable/c/1b050d09dd1a0ddae83bf012cf4956b7a960235f","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4131dd0b6f67acddd616ed7c244e1d3eedd46e7b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/6e0241f6cbb149d926ee8efee2c734fea71452cf","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/8ddc2eb0d2da9c83f54f1e5720525b461b8480c4","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/d981098b76756ed71666a27518eeb69883657c43","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f43ee0c0730d6191629b5ee1ceae27b1ebfdc047","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f93c89392bd3b180b5b7abc6fdae8e3dd667a313","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/fb29e1b41052488ee3f2d115d4a870497ebd7f7d","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-68138.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-68138"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2513343"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-68138"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-68138"},{"url":"https://lore.kernel.org/linux-cve-announce/2026081059-CVE-2026-68138-ffa7@gregkh/T"}],"tags":["nvd","exploit-available","csaf","vex","red-hat"],"epss":0.00283,"epssPercentile":0.21021,"ingestedAt":"2026-08-23T13:48:06.241Z","exploits":{"github":3,"githubRepos":["https://github.com/aramosf/CVE-2026-68138","https://github.com/suominen/CVE-2026-68138","https://github.com/jangkrikkbozz/CVE-2026-68138"],"checkedAt":"2026-09-23T07:14:37.345Z"},"exploitAvailable":true,"vendor":"Red Hat","product":"Red Hat Enterprise Linux 9","affected":["enterprise_linux 10","enterprise_linux 8","enterprise_linux 9","enterprise_linux_for_nvidia 26"],"cwe":["CWE-364"],"slug":"CVE-2026-68138","body":"## Overview\n\nIn 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat Enterprise Linux for NVIDIA 26 · no fix planned: Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat Enterprise Linux for NVIDIA 26 · updated 2026-09-22 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-68138.json)","depth":"midnight","depthScore":55,"depthScoreParts":{"impact":42.9,"likelihood":0.1,"exploitation":12,"ransomware":0},"changes":[{"seq":5434,"id":"CVE-2026-68138","ts":1788887282120,"field":"exploit_available","old":"false","new":"true"},{"seq":4317,"id":"CVE-2026-68138","ts":1788886395874,"field":"exploit_available","old":"true","new":"false"},{"seq":3055,"id":"CVE-2026-68138","ts":1788883059614,"field":"exploit_available","old":"false","new":"true"},{"seq":2084,"id":"CVE-2026-68138","ts":1788882464363,"field":"exploit_available","old":"true","new":"false"},{"seq":1150,"id":"CVE-2026-68138","ts":1788881901289,"field":"exploit_available","old":"false","new":"true"}]}