{"id":"CVE-2026-64036","state":"PUBLISHED","title":"cgroup/rstat: validate cpu before css_rstat_cpu() access","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ncgroup/rstat: validate cpu before css_rstat_cpu() access\n\ncss_rstat_updated() is exposed as a BPF kfunc and accepts a\ncaller-provided cpu argument. The function uses cpu for per-cpu rstat\nlookups without checking whether it refers to a valid possible CPU.\n\nA BPF iter/cgroup program with CAP_BPF and CAP_PERFMON can pass an\ninvalid cpu value. On an unfixed UBSCAN_BOUNDS test kernel, cpu ==\n0x7fffffff triggers:\n\n  UBSAN: array-index-out-of-bounds in kernel/cgroup/rstat.c:31:9\n  index 2147483647 is out of range for type 'long unsigned int [64]'\n  Call Trace:\n    css_rstat_updated\n    bpf_iter_run_prog\n    cgroup_iter_seq_show\n    bpf_seq_read\n\nAdd cpu validation to the BPF-facing css_rstat_updated() kfunc and\nmove the common implementation to __css_rstat_updated() for in-kernel\ncallers.","publishedAt":"2026-07-19T15:39:24.783Z","updatedAt":"2026-10-30T12:27:30.942Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"a319185be9f5ad13c2a296d448ac52ffe45d194c","status":"affected","lessThan":"ee5afb74688aa6f1f16d8c7e7b6bfaf803fb62fc","versionType":"git"},{"version":"a319185be9f5ad13c2a296d448ac52ffe45d194c","status":"affected","lessThan":"b28b862b07257219755d0b0a7fbe5d23b7c9ea91","versionType":"git"},{"version":"a319185be9f5ad13c2a296d448ac52ffe45d194c","status":"affected","lessThan":"3d595affbe00a2e8bf43b9f2947a8efcdc1c059e","versionType":"git"},{"version":"a319185be9f5ad13c2a296d448ac52ffe45d194c","status":"affected","lessThan":"6a01413a4e8fcb0263d7bef5075c5f8f4eb3a8b6","versionType":"git"},{"version":"a319185be9f5ad13c2a296d448ac52ffe45d194c","status":"affected","lessThan":"fd2bd9fa7700ddf28296486b2598cff2f80cc819","versionType":"git"},{"version":"a319185be9f5ad13c2a296d448ac52ffe45d194c","status":"affected","lessThan":"8817005efbdfdf5d4e4814cb5dc52b53d12917d7","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["block/blk-cgroup.c","include/linux/cgroup.h","kernel/cgroup/rstat.c","mm/memcontrol.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.1","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.34","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.11","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["block/blk-cgroup.c","include/linux/cgroup.h","kernel/cgroup/rstat.c","mm/memcontrol.c"]}],"references":["https://git.kernel.org/stable/c/ee5afb74688aa6f1f16d8c7e7b6bfaf803fb62fc","https://git.kernel.org/stable/c/b28b862b07257219755d0b0a7fbe5d23b7c9ea91","https://git.kernel.org/stable/c/3d595affbe00a2e8bf43b9f2947a8efcdc1c059e","https://git.kernel.org/stable/c/6a01413a4e8fcb0263d7bef5075c5f8f4eb3a8b6","https://git.kernel.org/stable/c/fd2bd9fa7700ddf28296486b2598cff2f80cc819","https://git.kernel.org/stable/c/8817005efbdfdf5d4e4814cb5dc52b53d12917d7"],"weaknesses":["CWE-125"],"ingestedAt":"2026-10-30T12:46:06.359Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/64xxx/CVE-2026-64036.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64036","state":"PUBLISHED","datePublished":"2026-07-19T15:39:24.783Z","dateUpdated":"2026-10-30T12:27:30.942Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T07:54:57.028Z"},"containers":{"cna":{"title":"cgroup/rstat: validate cpu before css_rstat_cpu() access","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ncgroup/rstat: validate cpu before css_rstat_cpu() access\n\ncss_rstat_updated() is exposed as a BPF kfunc and accepts a\ncaller-provided cpu argument. The function uses cpu for per-cpu rstat\nlookups without checking whether it refers to a valid possible CPU.\n\nA BPF iter/cgroup program with CAP_BPF and CAP_PERFMON can pass an\ninvalid cpu value. On an unfixed UBSCAN_BOUNDS test kernel, cpu ==\n0x7fffffff triggers:\n\n  UBSAN: array-index-out-of-bounds in kernel/cgroup/rstat.c:31:9\n  index 2147483647 is out of range for type 'long unsigned int [64]'\n  Call Trace:\n    css_rstat_updated\n    bpf_iter_run_prog\n    cgroup_iter_seq_show\n    bpf_seq_read\n\nAdd cpu validation to the BPF-facing css_rstat_updated() kfunc and\nmove the common implementation to __css_rstat_updated() for in-kernel\ncallers."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"a319185be9f5ad13c2a296d448ac52ffe45d194c","status":"affected","lessThan":"ee5afb74688aa6f1f16d8c7e7b6bfaf803fb62fc","versionType":"git"},{"version":"a319185be9f5ad13c2a296d448ac52ffe45d194c","status":"affected","lessThan":"b28b862b07257219755d0b0a7fbe5d23b7c9ea91","versionType":"git"},{"version":"a319185be9f5ad13c2a296d448ac52ffe45d194c","status":"affected","lessThan":"3d595affbe00a2e8bf43b9f2947a8efcdc1c059e","versionType":"git"},{"version":"a319185be9f5ad13c2a296d448ac52ffe45d194c","status":"affected","lessThan":"6a01413a4e8fcb0263d7bef5075c5f8f4eb3a8b6","versionType":"git"},{"version":"a319185be9f5ad13c2a296d448ac52ffe45d194c","status":"affected","lessThan":"fd2bd9fa7700ddf28296486b2598cff2f80cc819","versionType":"git"},{"version":"a319185be9f5ad13c2a296d448ac52ffe45d194c","status":"affected","lessThan":"8817005efbdfdf5d4e4814cb5dc52b53d12917d7","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["block/blk-cgroup.c","include/linux/cgroup.h","kernel/cgroup/rstat.c","mm/memcontrol.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.1","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.34","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.11","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["block/blk-cgroup.c","include/linux/cgroup.h","kernel/cgroup/rstat.c","mm/memcontrol.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/ee5afb74688aa6f1f16d8c7e7b6bfaf803fb62fc"},{"url":"https://git.kernel.org/stable/c/b28b862b07257219755d0b0a7fbe5d23b7c9ea91"},{"url":"https://git.kernel.org/stable/c/3d595affbe00a2e8bf43b9f2947a8efcdc1c059e"},{"url":"https://git.kernel.org/stable/c/6a01413a4e8fcb0263d7bef5075c5f8f4eb3a8b6"},{"url":"https://git.kernel.org/stable/c/fd2bd9fa7700ddf28296486b2598cff2f80cc819"},{"url":"https://git.kernel.org/stable/c/8817005efbdfdf5d4e4814cb5dc52b53d12917d7"}],"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 - Exploitation requires loading and running a BPF cgroup iterator/tracing program via local syscalls (bpf, read on iter fd); the call chain is css_rstat_updated → bpf_iter_run_prog → cgroup_iter_seq_show → bpf_seq_read, with no network-facing entry point.\nAC:L - The attacker fully controls the cpu argument passed from BPF (e.g. 0x7fffffff) and can trigger the bug deterministically on each iter read without races or victim-specific state.\nPR:L - Exploitation requires CAP_BPF and CAP_PERFMON to load and run BPF_PROG_TYPE_TRACING/cgroup-iter programs that can invoke the css_rstat_updated kfunc, as stated in the fix commit; these are elevated but not full init-namespace root privileges.\nUI:N - No victim interaction is required; the attacker triggers the bug by loading their own BPF program and reading from the attached iterator file descriptor.\nS:U - The vulnerability corrupts kernel memory from within kernel BPF context on the same host; it does not cross a VM/hypervisor or IOMMU security boundary.\nC:H - An invalid cpu indexes __per_cpu_offset[] out of bounds and yields a wild pointer used for structure reads (llist_on_list), enabling kernel memory disclosure beyond a bounded leak.\nI:H - The same out-of-bounds pointer is written via try_cmpxchg on llist_node.next and llist_add into a per-CPU list head, giving exploitable out-of-bounds kernel memory corruption.\nA:H - Operating on attacker-chosen out-of-bounds kernel addresses can cause kernel oops, panic, or hang during the corrupting cmpxchg/list operations."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:27:30.942Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"6.12.114"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"6.18.34"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"7.0.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-64036","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:35:47.371867Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-125","lang":"en","type":"CWE","description":"CWE-125 Out-of-bounds Read"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T20:28:10.231Z"}}]}}}