CVE-2025-39976

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2025-39976", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-04-16T07:20:57.150Z", "datePublished": "2025-10-15T07:55:57.608Z", "dateUpdated": "2026-08-05T12:06:45.033Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:06:45.033Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Use correct exit on failure from futex_hash_allocate_default()\n\ncopy_process() uses the wrong error exit path from futex_hash_allocate_default().\nAfter exiting from futex_hash_allocate_default(), neither tasklist_lock\nnor siglock has been acquired. The exit label bad_fork_core_free unlocks\nboth of these locks which is wrong.\n\nThe next exit label, bad_fork_cancel_cgroup, is the correct exit.\nsched_cgroup_fork() did not allocate any resources that need to freed.\n\nUse bad_fork_cancel_cgroup on error exit from futex_hash_allocate_default()."}], "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 through the clone()/clone3() syscall path (copy_process) combined with prctl(PR_FUTEX_HASH), both requiring local execution on the target system. There is no network-facing component in kernel/fork.c or kernel/futex/core.c.\nAC:L - The attacker fully controls both failure routes: forcing -ENOMEM on the GFP_KERNEL_ACCOUNT kvzalloc/alloc_percpu by sitting at a memcg limit is essentially deterministic, and the -EBUSY route is a race whose both sides (prctl PR_FUTEX_HASH_SET_SLOTS=0 and a clone(CLONE_VM) loop) are attacker-driven with unlimited retries. CONFIG_FUTEX_PRIVATE_HASH is default y on virtually all MMU builds, so no rare configuration is needed.\nPR:L - Any unprivileged local user can call pthread_create()/clone(CLONE_VM) and prctl(PR_FUTEX_HASH), neither of which has any capability check in kernel/sys.c or futex_hash_prctl(). No root, no namespace tricks, and no CAP_* are required.\nUI:N - The attacker triggers the faulty error path entirely from its own process via syscalls; no action by any other user or administrator is needed.\nS:U - The corrupted state (preempt_count, tasklist_lock, sighand->siglock, task/pid lists) is all within the kernel's own security authority on the same host. No hypervisor, IOMMU, or sandbox boundary is crossed.\nC:H - Spuriously releasing the global tasklist_lock and a shared sighand->siglock lets concurrent writers mutate the task list, thread list, pid hash, and signal structures simultaneously, producing list corruption and use-after-free of task_struct/sighand that can be groomed into a kernel memory read primitive. Per kernel scoring guidance, memory corruption leveragable for information disclosure is High.\nI:H - The stolen tasklist_lock/siglock permit racing list_add/list_del on global kernel structures, yielding dangling pointers and attacker-influenced writes, a classic path to control-flow hijack and privilege escalation. Additionally, preempt_count underflow leaves the CPU with corrupted context-tracking state that violates every atomicity assumption in the scheduler and RCU.\nA:H - Two unmatched preempt_enable() calls underflow the per-CPU preempt_count so the CPU permanently appears to be in hardirq/NMI context, breaking RCU, softirq processing, and preemption, which leads to RCU stalls, soft lockups, or panic; debug kernels BUG immediately on the bad unlock balance. Task-list corruption from the stolen tasklist_lock independently produces kernel oopses."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["kernel/fork.c"], "versions": [{"version": "7c4f75a21f636486d2969d9b6680403ea8483539", "lessThan": "f1635765cd0fdbf27b04d9a50be91a01b5adda13", "status": "affected", "versionType": "git"}, {"version": "7c4f75a21f636486d2969d9b6680403ea8483539", "lessThan": "4ec3c15462b9f44562f45723a92e2807746ba7d1", "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/fork.c"], "versions": [{"version": "6.16", "status": "affected"}, {"version": "0", "lessThan": "6.16", "status": "unaffected", "versionType": "semver"}, {"version": "6.16.10", "lessThanOrEqual": "6.16.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.17", "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": "6.16", "versionEndExcluding": "6.16.10"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.16", "versionEndExcluding": "6.17"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/f1635765cd0fdbf27b04d9a50be91a01b5adda13"}, {"url": "https://git.kernel.org/stable/c/4ec3c15462b9f44562f45723a92e2807746ba7d1"}], "title": "futex: Use correct exit on failure from futex_hash_allocate_default()", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["kernel/fork.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "f1635765cd0fdbf27b04d9a50be91a01b5adda13", "status": "affected", "version": "7c4f75a21f636486d2969d9b6680403ea8483539", "versionType": "git"}, {"lessThan": "4ec3c15462b9f44562f45723a92e2807746ba7d1", "status": "affected", "version": "7c4f75a21f636486d2969d9b6680403ea8483539", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["kernel/fork.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "6.16"}, {"lessThan": "6.16", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "6.16.*", "status": "unaffected", "version": "6.16.10", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "6.17", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Use correct exit on failure from futex_hash_allocate_default()\n\ncopy_process() uses the wrong error exit path from futex_hash_allocate_default().\nAfter exiting from futex_hash_allocate_default(), neither tasklist_lock\nnor siglock has been acquired. The exit label bad_fork_core_free unlocks\nboth of these locks which is wrong.\n\nThe next exit label, bad_fork_cancel_cgroup, is the correct exit.\nsched_cgroup_fork() did not allocate any resources that need to freed.\n\nUse bad_fork_cancel_cgroup on error exit from futex_hash_allocate_default()."}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nfutex: Usar la salida correcta en caso de fallo de futex_hash_allocate_default()\n\ncopy_process() utiliza la ruta de salida de error incorrecta de futex_hash_allocate_default(). Despu\u00e9s de salir de futex_hash_allocate_default(), ni tasklist_lock ni siglock han sido adquiridos. La etiqueta de salida bad_fork_core_free desbloquea ambos de estos bloqueos, lo cual es incorrecto.\n\nLa siguiente etiqueta de salida, bad_fork_cancel_cgroup, es la salida correcta. sched_cgroup_fork() no asign\u00f3 ning\u00fan recurso que necesite ser liberado.\n\nUsar bad_fork_cancel_cgroup en la salida de error de futex_hash_allocate_default()."}], "id": "CVE-2025-39976", "lastModified": "2026-10-19T21:10:00.160", "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": "2025-10-15T08:15:35.400", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/4ec3c15462b9f44562f45723a92e2807746ba7d1"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/f1635765cd0fdbf27b04d9a50be91a01b5adda13"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Deferred"}

{"bugzilla": {"description": "kernel: futex: Use correct exit on failure from futex_hash_allocate_default()", "id": "2404095", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2404095"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.0", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "details": ["In the Linux kernel, the following vulnerability has been resolved:\nfutex: Use correct exit on failure from futex_hash_allocate_default()\ncopy_process() uses the wrong error exit path from futex_hash_allocate_default().\nAfter exiting from futex_hash_allocate_default(), neither tasklist_lock\nnor siglock has been acquired. The exit label bad_fork_core_free unlocks\nboth of these locks which is wrong.\nThe next exit label, bad_fork_cancel_cgroup, is the correct exit.\nsched_cgroup_fork() did not allocate any resources that need to freed.\nUse bad_fork_cancel_cgroup on error exit from futex_hash_allocate_default()."], "name": "CVE-2025-39976", "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": "Out of support scope", "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": "2025-10-15T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-39976\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-39976\nhttps://lore.kernel.org/linux-cve-announce/2025101558-CVE-2025-39976-59ea@gregkh/T"], "threat_severity": "Moderate"}

{"created": "2025-10-20T13:27:14.559464+00:00", "updated": "2025-10-20T13:27:14.559490+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}