CVE-2026-43438

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It does not increment the reference counts on\nyielded css structs.\n\nAccording to the cgroup documentation, css_put() should only be used\nto release a reference obtained via css_get() or css_tryget_online().\nSince the iterator does not use either of these to acquire a reference,\ncalling css_put() in the error path of scx_cgroup_init() causes a\nrefcount underflow.\n\nRemove the unbalanced css_put() to prevent a potential Use-After-Free\n(UAF) vulnerability."}], "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 vulnerable path is reached from local userspace through BPF struct_ops scheduler registration and cgroup state, not by remote packets or adjacent/physical input.\nAC:L - An attacker with the needed BPF access can provide an ops.cgroup_init() callback that succeeds for root and fails for an existing non-root cgroup, directly triggering the bad error path without winning a race.\nPR:L - Loading and attaching sched_ext BPF struct_ops requires local BPF privileges, but these can be delegated via BPF tokens/user-namespace based capability checks in plausible deployments, so this is not necessarily real init-namespace root.\nUI:N - After the attacker has local access and the required BPF ability, exploitation is performed by their own syscalls and does not require a victim user action.\nS:U - The bug corrupts kernel cgroup/scheduler state within the same kernel security authority; it is not a VM escape or another explicit scope boundary crossing.\nC:H - The redundant css_put() can underflow the css refcount and lead to use-after-free of cgroup/task_group state, which is memory corruption that can plausibly enable kernel memory disclosure.\nI:H - A use-after-free in kernel heap-managed scheduler/cgroup objects can plausibly be shaped into arbitrary write or control-flow corruption, so integrity impact is high.\nA:H - Even without full exploitation, the refcount underflow/UAF can corrupt live kernel cgroup state and cause warnings, crashes, or panics."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["kernel/sched/ext.c"], "versions": [{"version": "8195136669661fdfe54e9a8923c33b31c92fc1da", "lessThan": "cc095cd305fddbe25a968e4a78436ff9476cf0f6", "status": "affected", "versionType": "git"}, {"version": "8195136669661fdfe54e9a8923c33b31c92fc1da", "lessThan": "6eaaa67d6998f6c30c462b140db8c062e07ec473", "status": "affected", "versionType": "git"}, {"version": "8195136669661fdfe54e9a8923c33b31c92fc1da", "lessThan": "bf50f3285eda8a0173625fcdb5f183f96e1008cd", "status": "affected", "versionType": "git"}, {"version": "8195136669661fdfe54e9a8923c33b31c92fc1da", "lessThan": "1336b579f6079fb8520be03624fcd9ba443c930b", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["kernel/sched/ext.c"], "versions": [{"version": "6.12", "status": "affected"}, {"version": "0", "lessThan": "6.12", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.78", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.19", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.19.9", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.0", "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": "6.12", "versionEndExcluding": "6.12.78"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12", "versionEndExcluding": "6.18.19"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12", "versionEndExcluding": "6.19.9"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12", "versionEndExcluding": "7.0"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/cc095cd305fddbe25a968e4a78436ff9476cf0f6"}, {"url": "https://git.kernel.org/stable/c/6eaaa67d6998f6c30c462b140db8c062e07ec473"}, {"url": "https://git.kernel.org/stable/c/bf50f3285eda8a0173625fcdb5f183f96e1008cd"}, {"url": "https://git.kernel.org/stable/c/1336b579f6079fb8520be03624fcd9ba443c930b"}], "title": "sched_ext: Remove redundant css_put() in scx_cgroup_init()", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["kernel/sched/ext.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "cc095cd305fddbe25a968e4a78436ff9476cf0f6", "status": "affected", "version": "8195136669661fdfe54e9a8923c33b31c92fc1da", "versionType": "git"}, {"lessThan": "6eaaa67d6998f6c30c462b140db8c062e07ec473", "status": "affected", "version": "8195136669661fdfe54e9a8923c33b31c92fc1da", "versionType": "git"}, {"lessThan": "bf50f3285eda8a0173625fcdb5f183f96e1008cd", "status": "affected", "version": "8195136669661fdfe54e9a8923c33b31c92fc1da", "versionType": "git"}, {"lessThan": "1336b579f6079fb8520be03624fcd9ba443c930b", "status": "affected", "version": "8195136669661fdfe54e9a8923c33b31c92fc1da", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["kernel/sched/ext.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "6.12"}, {"lessThan": "6.12", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "6.12.*", "status": "unaffected", "version": "6.12.78", "versionType": "semver"}, {"lessThanOrEqual": "6.18.*", "status": "unaffected", "version": "6.18.19", "versionType": "semver"}, {"lessThanOrEqual": "6.19.*", "status": "unaffected", "version": "6.19.9", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "7.0", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "CF16B1DB-0D79-4F76-8B3C-57C79AB99F70", "versionEndExcluding": "6.12.78", "versionStartIncluding": "6.12", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "D394AC60-6F28-435F-872A-CCDF384B8331", "versionEndExcluding": "6.18.19", "versionStartIncluding": "6.13", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "E825E7C3-FEAC-4FD3-8A81-78D7387948C9", "versionEndExcluding": "6.19.9", "versionStartIncluding": "6.19", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*", "matchCriteriaId": "4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Remove redundant css_put() in scx_cgroup_init()\n\nThe iterator css_for_each_descendant_pre() walks the cgroup hierarchy\nunder cgroup_lock(). It does not increment the reference counts on\nyielded css structs.\n\nAccording to the cgroup documentation, css_put() should only be used\nto release a reference obtained via css_get() or css_tryget_online().\nSince the iterator does not use either of these to acquire a reference,\ncalling css_put() in the error path of scx_cgroup_init() causes a\nrefcount underflow.\n\nRemove the unbalanced css_put() to prevent a potential Use-After-Free\n(UAF) vulnerability."}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nsched_ext: Eliminar css_put() redundante en scx_cgroup_init()\n\nEl iterador css_for_each_descendant_pre() recorre la jerarqu\u00eda de cgroup bajo cgroup_lock(). No incrementa los recuentos de referencia en las estructuras css generadas.\n\nSeg\u00fan la documentaci\u00f3n de cgroup, css_put() solo debe usarse para liberar una referencia obtenida a trav\u00e9s de css_get() o css_tryget_online(). Dado que el iterador no usa ninguna de estas para adquirir una referencia, llamar a css_put() en la ruta de error de scx_cgroup_init() causa un subdesbordamiento del contador de referencias.\n\nEliminar el css_put() desequilibrado para prevenir una potencial vulnerabilidad de Uso despu\u00e9s de liberaci\u00f3n (UAF)."}], "id": "CVE-2026-43438", "lastModified": "2026-11-11T20:10:00.273", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}]}, "published": "2026-05-08T15:16:56.160", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/1336b579f6079fb8520be03624fcd9ba443c930b"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/6eaaa67d6998f6c30c462b140db8c062e07ec473"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/bf50f3285eda8a0173625fcdb5f183f96e1008cd"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/cc095cd305fddbe25a968e4a78436ff9476cf0f6"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-416"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: sched_ext: Remove redundant css_put() in scx_cgroup_init()", "id": "2468235", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2468235"}, "csaw": false, "cwe": "CWE-1341", "details": ["A flaw was found in the Linux kernel's sched_ext component. This vulnerability is caused by a redundant `css_put()` call in the `scx_cgroup_init()` function, leading to a reference count underflow. This can result in a Use-After-Free (UAF) vulnerability, potentially allowing a local attacker to cause a denial of service or achieve privilege escalation."], "name": "CVE-2026-43438", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-05-08T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-43438\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-43438\nhttps://lore.kernel.org/linux-cve-announce/2026050853-CVE-2026-43438-f2f2@gregkh/T"]}

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