CVE-2026-31786

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It is not reachable directly from network packets or adjacent/physical interfaces.\nAC:L - Triggering the bug only requires reading a sysfs file, with no race or special timing. Any uncertainty about heap layout affects exploitation details, so the higher-severity low complexity is appropriate.\nPR:L - The sysfs attribute is read-only mode 0444, so any unprivileged local user in the Xen guest can access it. No capability, authentication, or real-root check gates the read path.\nUI:N - No victim action is required beyond the attacker performing the sysfs read. The vulnerable code runs synchronously in the attacker's read path.\nS:U - The impact is within the Linux Xen guest kernel security authority. This is not a Xen guest-to-host escape or cross-VM boundary violation.\nC:H - The bug performs an out-of-bounds read past the hypervisor build ID and can return adjacent kernel memory through a user-readable sysfs file. The Xen advisory states kernel secrets may be leaked.\nI:H - If no NUL byte is encountered before the PAGE_SIZE sysfs buffer is exceeded, sprintf can write past the sysfs buffer and corrupt kernel memory. The advisory identifies privilege escalation as possible, so high integrity impact is defensible.\nA:H - The out-of-bounds read/write can corrupt kernel memory and crash the guest kernel. The advisory explicitly lists DoS as a possible impact."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["drivers/xen/sys-hypervisor.c"], "versions": [{"version": "84b7625728ea311ea35bdaa0eded53c1c56baeaa", "lessThan": "e3af585e1728c917682b6a3de9a69b41fb9194d4", "status": "affected", "versionType": "git"}, {"version": "84b7625728ea311ea35bdaa0eded53c1c56baeaa", "lessThan": "8288d031a01dbacfde3fc643f7be3d23504de64d", "status": "affected", "versionType": "git"}, {"version": "84b7625728ea311ea35bdaa0eded53c1c56baeaa", "lessThan": "f458ba102da97fafca106327086fc95f3fc764cb", "status": "affected", "versionType": "git"}, {"version": "84b7625728ea311ea35bdaa0eded53c1c56baeaa", "lessThan": "4b4defd2fce3f966c25adabf46644a85558f1169", "status": "affected", "versionType": "git"}, {"version": "84b7625728ea311ea35bdaa0eded53c1c56baeaa", "lessThan": 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It is not reachable directly from network packets or adjacent/physical interfaces.\nAC:L - Triggering the bug only requires reading a sysfs file, with no race or special timing. Any uncertainty about heap layout affects exploitation details, so the higher-severity low complexity is appropriate.\nPR:L - The sysfs attribute is read-only mode 0444, so any unprivileged local user in the Xen guest can access it. No capability, authentication, or real-root check gates the read path.\nUI:N - No victim action is required beyond the attacker performing the sysfs read. The vulnerable code runs synchronously in the attacker's read path.\nS:U - The impact is within the Linux Xen guest kernel security authority. This is not a Xen guest-to-host escape or cross-VM boundary violation.\nC:H - The bug performs an out-of-bounds read past the hypervisor build ID and can return adjacent kernel memory through a user-readable sysfs file. The Xen advisory states kernel secrets may be leaked.\nI:H - If no NUL byte is encountered before the PAGE_SIZE sysfs buffer is exceeded, sprintf can write past the sysfs buffer and corrupt kernel memory. The advisory identifies privilege escalation as possible, so high integrity impact is defensible.\nA:H - The out-of-bounds read/write can corrupt kernel memory and crash the guest kernel. The advisory explicitly lists DoS as a possible impact."}]}], "affected": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "84b7625728ea311ea35bdaa0eded53c1c56baeaa", "lessThan": "e3af585e1728c917682b6a3de9a69b41fb9194d4", "versionType": "git"}, {"status": "affected", "version": "84b7625728ea311ea35bdaa0eded53c1c56baeaa", "lessThan": "8288d031a01dbacfde3fc643f7be3d23504de64d", "versionType": "git"}, {"status": "affected", "version": "84b7625728ea311ea35bdaa0eded53c1c56baeaa", "lessThan": "f458ba102da97fafca106327086fc95f3fc764cb", "versionType": "git"}, {"status": "affected", "version": "84b7625728ea311ea35bdaa0eded53c1c56baeaa", "lessThan": "4b4defd2fce3f966c25adabf46644a85558f1169", "versionType": "git"}, {"status": "affected", "version": "84b7625728ea311ea35bdaa0eded53c1c56baeaa", "lessThan": "5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0a", "versionType": "git"}, {"status": 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"https://git.kernel.org/stable/c/4b4defd2fce3f966c25adabf46644a85558f1169"}, {"url": "https://git.kernel.org/stable/c/5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0a"}, {"url": "https://git.kernel.org/stable/c/d5f59216650c51e5e3fcb7517c825bc8047f60ef"}, {"url": "https://git.kernel.org/stable/c/52cecff98bda2c51eed1c6ce9d21c5d6268fb19d"}, {"url": "https://git.kernel.org/stable/c/27fdbab4221b375de54bf91919798d88520c6e28"}], "x_generator": {"engine": "bippy-1.2.0"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nBuffer overflow in drivers/xen/sys-hypervisor.c\n\nThe build id returned by HYPERVISOR_xen_version(XENVER_build_id) is\nneither NUL terminated nor a string.\n\nThe first causes a buffer overflow as sprintf in buildid_show will\nread and copy till it finds a NUL.\n\n00000000 f4 91 51 f4 dd 38 9e 9d 65 47 52 eb 10 71 db 50 |..Q..8..eGR..q.P|\n00000010 b9 a8 01 42 6f 2e 32 |...Bo.2|\n00000017\n\nSo use a memcpy instead of sprintf to have the correct value:\n\n00000000 f4 91 51 f4 dd 00 9e 9d 65 47 52 eb 10 71 db 50 |..Q.....eGR..q.P|\n00000010 b9 a8 01 42 |...B|\n00000014\n\n(the above have a hack to embed a zero inside and check it's\nreturned correctly).\n\nThis is XSA-485 / CVE-2026-31786"}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.10.254", "versionStartIncluding": "4.13"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.15.204", "versionStartIncluding": "4.13"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.1.170", "versionStartIncluding": "4.13"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.6.137", "versionStartIncluding": "4.13"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", 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true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "FA800016-0012-4E3F-A528-2A7F378A0A4A", "versionEndExcluding": "5.15.204", "versionStartIncluding": "5.11", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "E6653854-B188-42DD-B8C5-0143F1956AB1", "versionEndExcluding": "6.1.170", "versionStartIncluding": "5.16", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "3CA3EF52-168A-4348-8F5F-356C9EB69261", "versionEndExcluding": "6.6.137", "versionStartIncluding": "6.2", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "F17D292D-A9B5-4DC7-8002-51AB95335606", "versionEndExcluding": "6.12.85", "versionStartIncluding": "6.7", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "85751F83-26BA-498C-90E7-E38A59C4564D", "versionEndExcluding": "6.18.26", "versionStartIncluding": "6.13", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "C7C9A567-4F4F-4C61-BAD3-440B34C67118", "versionEndExcluding": "7.0.3", "versionStartIncluding": "6.19", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:*", "matchCriteriaId": "B1EF7059-E670-45F4-B422-54C40FA86390", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:*", "matchCriteriaId": "0D38F0BF-A728-4133-A358-D44A2F7EE6D6", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nBuffer overflow in drivers/xen/sys-hypervisor.c\n\nThe build id returned by HYPERVISOR_xen_version(XENVER_build_id) is\nneither NUL terminated nor a string.\n\nThe first causes a buffer overflow as sprintf in buildid_show will\nread and copy till it finds a NUL.\n\n00000000 f4 91 51 f4 dd 38 9e 9d 65 47 52 eb 10 71 db 50 |..Q..8..eGR..q.P|\n00000010 b9 a8 01 42 6f 2e 32 |...Bo.2|\n00000017\n\nSo use a memcpy instead of sprintf to have the correct value:\n\n00000000 f4 91 51 f4 dd 00 9e 9d 65 47 52 eb 10 71 db 50 |..Q.....eGR..q.P|\n00000010 b9 a8 01 42 |...B|\n00000014\n\n(the above have a hack to embed a zero inside and check it's\nreturned correctly).\n\nThis is XSA-485 / CVE-2026-31786"}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nDesbordamiento de b\u00fafer en drivers/xen/sys-hypervisor.c\n\nEl ID de compilaci\u00f3n devuelto por HYPERVISOR_xen_version(XENVER_build_id) no est\u00e1 terminado en NUL ni es una cadena.\n\nEl primero causa un desbordamiento de b\u00fafer ya que sprintf en buildid_show leer\u00e1 y copiar\u00e1 hasta que encuentre un NUL.\n\n00000000 f4 91 51 f4 dd 38 9e 9d 65 47 52 eb 10 71 db 50 |..Q..8..eGR..q.P|\n00000010 b9 a8 01 42 6f 2e 32 |...Bo.2|\n00000017\n\nAs\u00ed que use un memcpy en lugar de sprintf para tener el valor correcto:\n\n00000000 f4 91 51 f4 dd 00 9e 9d 65 47 52 eb 10 71 db 50 |..Q.....eGR..q.P|\n00000010 b9 a8 01 42 |...B|\n00000014\n\n(lo anterior tiene un truco para incrustar un cero dentro y verificar que se devuelve correctamente).\n\nEsto es XSA-485 / CVE-2026-31786"}], "id": "CVE-2026-31786", "lastModified": "2026-11-11T21:10:00.200", "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"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-31786", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-10-16T15:13:16.479800Z", "version": "2.0.3"}}]}, "published": "2026-04-30T11:16:20.967", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/27fdbab4221b375de54bf91919798d88520c6e28"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/4b4defd2fce3f966c25adabf46644a85558f1169"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/52cecff98bda2c51eed1c6ce9d21c5d6268fb19d"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0a"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/8288d031a01dbacfde3fc643f7be3d23504de64d"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/d5f59216650c51e5e3fcb7517c825bc8047f60ef"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/e3af585e1728c917682b6a3de9a69b41fb9194d4"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/f458ba102da97fafca106327086fc95f3fc764cb"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Mailing List", "Third Party Advisory"], "url": "http://www.openwall.com/lists/oss-security/2026/04/28/12"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Mailing List", "Third Party Advisory"], "url": "http://xenbits.xen.org/xsa/advisory-485.html"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-787"}], "source": "nvd@nist.gov", "type": "Primary"}, {"description": [{"lang": "en", "value": "CWE-120"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{"bugzilla": {"description": "kernel: Buffer overflow in drivers/xen/sys-hypervisor.c", "id": "2464096", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2464096"}, "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"}, "cwe": "CWE-170", "details": ["A flaw was found in the Linux kernel. A buffer overflow vulnerability exists in the Xen hypervisor driver (`drivers/xen/sys-hypervisor.c`). This flaw occurs because the `HYPERVISOR_xen_version(XENVER_build_id)` function returns a build ID that is not properly null-terminated. When the `buildid_show` function attempts to process this non-null-terminated string using `sprintf`, it can read and copy beyond the intended buffer boundary, potentially leading to a denial of service or other unspecified impacts."], "name": "CVE-2026-31786", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Under investigation", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-04-30T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-31786\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-31786\nhttps://lore.kernel.org/linux-cve-announce/2026043031-CVE-2026-31786-826a@gregkh/T"], "threat_severity": "Important"}

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