CVE-2026-31786
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: Buffer overflow in drivers/xen/sys-hypervisor.c The build id returned by HYPERVISOR_xen_version(XENVER_build_id) is neither NUL terminated nor a string. The first causes a buffer overflow as sprintf in buildid_show will read and copy till it finds a NUL. 00000000 f4 91 51 f4 dd 38 9e 9d 65 47 52 eb 10 71 db 50 |..Q..8..eGR..q.P| 00000010 b9 a8 01 42 6f 2e 32 |...Bo.2| 00000017 So use a memcpy instead of sprintf to have the correct value: 00000000 f4 91 51 f4 dd 00 9e 9d 65 47 52 eb 10 71 db 50 |..Q.....eGR..q.P| 00000010 b9 a8 01 42 |...B| 00000014 (the above have a hack to embed a zero inside and check it's returned correctly). This is XSA-485 / CVE-2026-31786
Severity
HIGH
CVSS score
7.8
(v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2026-04-30 11:16:20.967000
Last modified
2026-10-19 20:17:59.360000
View original CVE JSON
{
"id": "CVE-2026-31786",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-04-30T11:16:20.967",
"lastModified": "2026-10-19T20:17:59.360",
"vulnStatus": "Modified",
"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"
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"drivers/xen/sys-hypervisor.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"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": "affected"
},
{
"version": "84b7625728ea311ea35bdaa0eded53c1c56baeaa",
"lessThan": "d5f59216650c51e5e3fcb7517c825bc8047f60ef",
"versionType": "git",
"status": "affected"
},
{
"version": "84b7625728ea311ea35bdaa0eded53c1c56baeaa",
"lessThan": "52cecff98bda2c51eed1c6ce9d21c5d6268fb19d",
"versionType": "git",
"status": "affected"
},
{
"version": "84b7625728ea311ea35bdaa0eded53c1c56baeaa",
"lessThan": "27fdbab4221b375de54bf91919798d88520c6e28",
"versionType": "git",
"status": "affected"
}
]
},
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "affected",
"programFiles": [
"drivers/xen/sys-hypervisor.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "4.13",
"status": "affected"
},
{
"version": "0",
"lessThan": "4.13",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "5.10.254",
"lessThanOrEqual": "5.10.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "5.15.204",
"lessThanOrEqual": "5.15.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.1.170",
"lessThanOrEqual": "6.1.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.6.137",
"lessThanOrEqual": "6.6.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.12.85",
"lessThanOrEqual": "6.12.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.18.26",
"lessThanOrEqual": "6.18.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.0.3",
"lessThanOrEqual": "7.0.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.1",
"lessThanOrEqual": "*",
"versionType": "original_commit_for_fix",
"status": "unaffected"
}
]
}
]
}
],
"metrics": {
"cvssMetricV31": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary",
"cvssData": {
"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",
"attackVector": "LOCAL",
"attackComplexity": "LOW",
"privilegesRequired": "LOW",
"userInteraction": "NONE",
"scope": "UNCHANGED",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"availabilityImpact": "HIGH"
},
"exploitabilityScore": 1.8,
"impactScore": 5.9
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"timestamp": "2026-10-16T15:13:16.479800Z",
"id": "CVE-2026-31786",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "total"
}
],
"role": "CISA Coordinator",
"version": "2.0.3"
}
}
]
},
"weaknesses": [
{
"source": "[email protected]",
"type": "Primary",
"description": [
{
"lang": "en",
"value": "CWE-787"
}
]
},
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"type": "Secondary",
"description": [
{
"lang": "en",
"value": "CWE-120"
}
]
}
],
"configurations": [
{
"nodes": [
{
"operator": "OR",
"negate": false,
"cpeMatch": [
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "4.13",
"versionEndExcluding": "5.10.254",
"matchCriteriaId": "1493839B-26E7-4663-8942-B55262171032"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.11",
"versionEndExcluding": "5.15.204",
"matchCriteriaId": "FA800016-0012-4E3F-A528-2A7F378A0A4A"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.16",
"versionEndExcluding": "6.1.170",
"matchCriteriaId": "E6653854-B188-42DD-B8C5-0143F1956AB1"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "6.2",
"versionEndExcluding": "6.6.137",
"matchCriteriaId": "3CA3EF52-168A-4348-8F5F-356C9EB69261"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "6.7",
"versionEndExcluding": "6.12.85",
"matchCriteriaId": "F17D292D-A9B5-4DC7-8002-51AB95335606"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "6.13",
"versionEndExcluding": "6.18.26",
"matchCriteriaId": "85751F83-26BA-498C-90E7-E38A59C4564D"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "6.19",
"versionEndExcluding": "7.0.3",
"matchCriteriaId": "C7C9A567-4F4F-4C61-BAD3-440B34C67118"
},
{
"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"
}
]
}
]
}
],
"references": [
{
"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": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
]
},
{
"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",
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
"Mailing List",
"Third Party Advisory"
]
}
]
}