CVE-2025-39815

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No race, no memory-layout guessing, and no condition outside the attacker's control on an affected RISC-V host with the V extension.\nPR:L - No capable()/CAP_SYS_ADMIN check exists anywhere on the path \u2014 only opening /dev/kvm and creating a VM/vCPU, which unprivileged users in the kvm group and sandboxed VMM processes (QEMU, crosvm) routinely have. The confined VMM process itself is the natural attacker here.\nUI:N - The attacking process performs the ioctl entirely on its own; no victim action, mount, or file open is needed.\nS:U - The attacker is host userspace and the corrupted memory is the host kernel stack of its own task \u2014 the same security authority, i.e. standard kernel privilege escalation rather than a guest-to-host or IOMMU boundary crossing.\nC:H - The attacker-controlled stack smash overwrites saved registers, frame pointers and return addresses, which is a classic route to control-flow hijack and hence arbitrary kernel memory disclosure. Per kernel scoring guidance, memory corruption leverageable for info disclosure is High.\nI:H - This is an out-of-bounds kernel stack write of up to ~32 KB with fully attacker-chosen contents and length, directly overwriting return addresses and adjacent frames \u2014 an arbitrary-write/code-execution primitive.\nA:H - Even without exploitation, overrunning the 16 KB RISC-V kernel stack reliably corrupts the stack canary, return addresses, or the VMAP guard page, producing an immediate kernel panic that any user with /dev/kvm access can trigger at will."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["arch/riscv/kvm/vcpu_vector.c"], "versions": [{"version": "2fa290372dfe7dd248b1c16f943f273a3e674f22", "lessThan": "c76bf8359188a11f8fd790e5bbd6077894a245cc", "status": "affected", "versionType": "git"}, {"version": "2fa290372dfe7dd248b1c16f943f273a3e674f22", "lessThan": "6d28659b692a0212f360f8bd8a58712b339f9aac", "status": "affected", "versionType": "git"}, {"version": "2fa290372dfe7dd248b1c16f943f273a3e674f22", "lessThan": "799766208f09f95677a9ab111b93872d414fbad7", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["arch/riscv/kvm/vcpu_vector.c"], "versions": [{"version": "6.8", "status": "affected"}, {"version": "0", "lessThan": "6.8", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.45", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.16.5", "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": "6.8", "versionEndExcluding": "6.12.45"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.8", "versionEndExcluding": "6.16.5"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.8", "versionEndExcluding": "6.17"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/c76bf8359188a11f8fd790e5bbd6077894a245cc"}, {"url": "https://git.kernel.org/stable/c/6d28659b692a0212f360f8bd8a58712b339f9aac"}, {"url": "https://git.kernel.org/stable/c/799766208f09f95677a9ab111b93872d414fbad7"}], "title": "RISC-V: KVM: fix stack overrun when loading vlenb", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"metrics": [{"cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 5.5, "attackVector": "LOCAL", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "NONE"}}, {"other": {"type": "ssvc", "content": {"id": "CVE-2025-39815", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-01-14T18:15:40.818434Z"}}}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "description": "CWE-noinfo Not enough information"}]}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-01-14T18:22:55.580Z"}}]}}

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We want only xlen bits, so check the size beforehand."}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nRISC-V: KVM: correcci\u00f3n de desbordamiento de pila al cargar vlenb\n\nLa carga del espacio de usuario puede introducir hasta 2048 bits en un b\u00fafer de pila de xlen bits. Solo queremos xlen bits, as\u00ed que se comprueba el tama\u00f1o de antemano."}], "id": "CVE-2025-39815", "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"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 5.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 5.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 3.6, "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2025-39815", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-01-14T18:15:40.818434Z", "version": "2.0.3"}}]}, "published": "2025-09-16T13:15:56.240", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/6d28659b692a0212f360f8bd8a58712b339f9aac"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/799766208f09f95677a9ab111b93872d414fbad7"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/c76bf8359188a11f8fd790e5bbd6077894a245cc"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "NVD-CWE-noinfo"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: RISC-V: KVM: fix stack overrun when loading vlenb", "id": "2395789", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2395789"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.5", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "details": ["No description is available for this CVE."], "name": "CVE-2025-39815", "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": "2025-09-16T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-39815\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-39815\nhttps://lore.kernel.org/linux-cve-announce/2025091615-CVE-2025-39815-a663@gregkh/T"], "threat_severity": "Moderate"}

{"created": "2025-09-17T10:04:16.135451+00:00", "updated": "2025-09-17T10:04:16.135483+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}