{"id":"CVE-2026-31786","state":"PUBLISHED","title":"Buffer overflow in drivers/xen/sys-hypervisor.c","description":"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","publishedAt":"2026-04-30T10:31:28.293Z","updatedAt":"2026-10-19T19:06:08.809Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"84b7625728ea311ea35bdaa0eded53c1c56baeaa","status":"affected","lessThan":"e3af585e1728c917682b6a3de9a69b41fb9194d4","versionType":"git"},{"version":"84b7625728ea311ea35bdaa0eded53c1c56baeaa","status":"affected","lessThan":"8288d031a01dbacfde3fc643f7be3d23504de64d","versionType":"git"},{"version":"84b7625728ea311ea35bdaa0eded53c1c56baeaa","status":"affected","lessThan":"f458ba102da97fafca106327086fc95f3fc764cb","versionType":"git"},{"version":"84b7625728ea311ea35bdaa0eded53c1c56baeaa","status":"affected","lessThan":"4b4defd2fce3f966c25adabf46644a85558f1169","versionType":"git"},{"version":"84b7625728ea311ea35bdaa0eded53c1c56baeaa","status":"affected","lessThan":"5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0a","versionType":"git"},{"version":"84b7625728ea311ea35bdaa0eded53c1c56baeaa","status":"affected","lessThan":"d5f59216650c51e5e3fcb7517c825bc8047f60ef","versionType":"git"},{"version":"84b7625728ea311ea35bdaa0eded53c1c56baeaa","status":"affected","lessThan":"52cecff98bda2c51eed1c6ce9d21c5d6268fb19d","versionType":"git"},{"version":"84b7625728ea311ea35bdaa0eded53c1c56baeaa","status":"affected","lessThan":"27fdbab4221b375de54bf91919798d88520c6e28","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/xen/sys-hypervisor.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.13","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.13","versionType":"semver"},{"version":"5.10.254","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.204","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.170","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.137","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.85","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.26","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.3","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/xen/sys-hypervisor.c"]}],"references":["https://git.kernel.org/stable/c/e3af585e1728c917682b6a3de9a69b41fb9194d4","https://git.kernel.org/stable/c/8288d031a01dbacfde3fc643f7be3d23504de64d","https://git.kernel.org/stable/c/f458ba102da97fafca106327086fc95f3fc764cb","https://git.kernel.org/stable/c/4b4defd2fce3f966c25adabf46644a85558f1169","https://git.kernel.org/stable/c/5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0a","https://git.kernel.org/stable/c/d5f59216650c51e5e3fcb7517c825bc8047f60ef","https://git.kernel.org/stable/c/52cecff98bda2c51eed1c6ce9d21c5d6268fb19d","https://git.kernel.org/stable/c/27fdbab4221b375de54bf91919798d88520c6e28","http://www.openwall.com/lists/oss-security/2026/04/28/12","http://xenbits.xen.org/xsa/advisory-485.html"],"weaknesses":["CWE-120"],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/31xxx/CVE-2026-31786.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-31786","state":"PUBLISHED","datePublished":"2026-04-30T10:31:28.293Z","dateUpdated":"2026-10-19T19:06:08.809Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-03-09T15:48:24.141Z"},"containers":{"cna":{"title":"Buffer overflow in drivers/xen/sys-hypervisor.c","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":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"84b7625728ea311ea35bdaa0eded53c1c56baeaa","status":"affected","lessThan":"e3af585e1728c917682b6a3de9a69b41fb9194d4","versionType":"git"},{"version":"84b7625728ea311ea35bdaa0eded53c1c56baeaa","status":"affected","lessThan":"8288d031a01dbacfde3fc643f7be3d23504de64d","versionType":"git"},{"version":"84b7625728ea311ea35bdaa0eded53c1c56baeaa","status":"affected","lessThan":"f458ba102da97fafca106327086fc95f3fc764cb","versionType":"git"},{"version":"84b7625728ea311ea35bdaa0eded53c1c56baeaa","status":"affected","lessThan":"4b4defd2fce3f966c25adabf46644a85558f1169","versionType":"git"},{"version":"84b7625728ea311ea35bdaa0eded53c1c56baeaa","status":"affected","lessThan":"5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0a","versionType":"git"},{"version":"84b7625728ea311ea35bdaa0eded53c1c56baeaa","status":"affected","lessThan":"d5f59216650c51e5e3fcb7517c825bc8047f60ef","versionType":"git"},{"version":"84b7625728ea311ea35bdaa0eded53c1c56baeaa","status":"affected","lessThan":"52cecff98bda2c51eed1c6ce9d21c5d6268fb19d","versionType":"git"},{"version":"84b7625728ea311ea35bdaa0eded53c1c56baeaa","status":"affected","lessThan":"27fdbab4221b375de54bf91919798d88520c6e28","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/xen/sys-hypervisor.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.13","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.13","versionType":"semver"},{"version":"5.10.254","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.204","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.170","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.137","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.85","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.26","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.3","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/xen/sys-hypervisor.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/e3af585e1728c917682b6a3de9a69b41fb9194d4"},{"url":"https://git.kernel.org/stable/c/8288d031a01dbacfde3fc643f7be3d23504de64d"},{"url":"https://git.kernel.org/stable/c/f458ba102da97fafca106327086fc95f3fc764cb"},{"url":"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"}],"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 buildid_show path is reached by a local read of /sys/hypervisor/properties/buildid inside a Linux Xen domain. 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."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:25:11.040Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.13","versionEndExcluding":"5.10.254"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.13","versionEndExcluding":"5.15.204"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.13","versionEndExcluding":"6.1.170"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.13","versionEndExcluding":"6.6.137"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.13","versionEndExcluding":"6.12.85"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.13","versionEndExcluding":"6.18.26"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.13","versionEndExcluding":"7.0.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.13","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CVE Program Container","references":[{"url":"http://www.openwall.com/lists/oss-security/2026/04/28/12"},{"url":"http://xenbits.xen.org/xsa/advisory-485.html"}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2026-04-30T10:39:32.708Z"}},{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-31786","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:13:16.479800Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-120","lang":"en","type":"CWE","description":"CWE-120 Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T19:06:08.809Z"}}]}}}