{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-31788", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-03-09T15:48:24.141Z", "datePublished": "2026-03-25T10:25:05.542Z", "dateUpdated": "2026-08-05T12:25:12.114Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:25:12.114Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxen/privcmd: restrict usage in unprivileged domU\n\nThe Xen privcmd driver allows to issue arbitrary hypercalls from\nuser space processes. This is normally no problem, as access is\nusually limited to root and the hypervisor will deny any hypercalls\naffecting other domains.\n\nIn case the guest is booted using secure boot, however, the privcmd\ndriver would be enabling a root user process to modify e.g. kernel\nmemory contents, thus breaking the secure boot feature.\n\nThe only known case where an unprivileged domU is really needing to\nuse the privcmd driver is the case when it is acting as the device\nmodel for another guest. In this case all hypercalls issued via the\nprivcmd driver will target that other guest.\n\nFortunately the privcmd driver can already be locked down to allow\nonly hypercalls targeting a specific domain, but this mode can be\nactivated from user land only today.\n\nThe target domain can be obtained from Xenstore, so when not running\nin dom0 restrict the privcmd driver to that target domain from the\nbeginning, resolving the potential problem of breaking secure boot.\n\nThis is XSA-482\n\n---\nV2:\n- defer reading from Xenstore if Xenstore isn't ready yet (Jan Beulich)\n- wait in open() if target domain isn't known yet\n- issue message in case no target domain found (Jan Beulich)" } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H", "baseScore": 8.2, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The attacker must have local access to the Xen guest VM to open /dev/xen/privcmd and issue ioctls. This is a local device file accessed via ioctl.\nAC:L - The attacker can reliably open /dev/xen/privcmd and issue arbitrary hypercalls via IOCTL_PRIVCMD_HYPERCALL. No special conditions or race timing required.\nPR:H - The /dev/xen/privcmd device is typically restricted to root access. The attacker needs root privileges within the Xen guest VM, and this cannot be obtained through user namespaces since it requires real access to the Xen device node.\nUI:N - No user interaction is required. The root attacker in the guest VM can directly open the device and issue hypercalls without any victim action.\nS:C - This vulnerability allows bypassing Secure Boot/Lockdown protections. A root user who should be constrained by Secure Boot from modifying kernel memory can use privcmd hypercalls to cross that security boundary and modify kernel memory, defeating the Lockdown security model.\nC:H - Arbitrary hypercalls can be used to read kernel memory contents in the guest, providing full confidentiality compromise of kernel data that Secure Boot/Lockdown is designed to protect.\nI:H - The commit explicitly states the vulnerability allows \"a root user process to modify e.g. kernel memory contents.\" Arbitrary hypercalls enable writing to kernel memory, providing full integrity compromise.\nA:H - With the ability to issue arbitrary hypercalls and modify kernel memory, the attacker can crash the guest kernel or cause denial of service trivially." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/xen/privcmd.c" ], "versions": [ { "version": "1c5de1939c204bde9cce87f4eb3d26e9f9eb732b", "lessThan": "4eb245ff0d33b618e097a2c23de5df56d4ad6969", "status": "affected", "versionType": "git" }, { "version": "1c5de1939c204bde9cce87f4eb3d26e9f9eb732b", "lessThan": "3ee5b9e3de4b8bdd74183d83205481c91a9effc8", "status": "affected", "versionType": "git" }, { "version": "1c5de1939c204bde9cce87f4eb3d26e9f9eb732b", "lessThan": "87a803edb2ded911cb587c53bff179d2a2ed2a28", "status": "affected", "versionType": "git" }, { "version": "1c5de1939c204bde9cce87f4eb3d26e9f9eb732b", "lessThan": "1879319d790f7d57622cdc22807b60ea78b56b6d", "status": "affected", "versionType": "git" }, { "version": "1c5de1939c204bde9cce87f4eb3d26e9f9eb732b", "lessThan": "78432d8f0372c71c518096395537fa12be7ff24e", "status": "affected", "versionType": "git" }, { "version": "1c5de1939c204bde9cce87f4eb3d26e9f9eb732b", "lessThan": "389bae9a4409934e8b8d4dbdaaf02a3ae71cf8e4", "status": "affected", "versionType": "git" }, { "version": "1c5de1939c204bde9cce87f4eb3d26e9f9eb732b", "lessThan": "cbede2e833da1893afbea9b3ff29b5dda23a4a91", "status": "affected", "versionType": "git" }, { "version": "1c5de1939c204bde9cce87f4eb3d26e9f9eb732b", "lessThan": "453b8fb68f3641fea970db88b7d9a153ed2a37e8", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/xen/privcmd.c" ], "versions": [ { "version": "2.6.37", "status": "affected" }, { "version": "0", "lessThan": "2.6.37", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.253", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.203", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.167", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.130", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.78", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.20", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.19.10", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0", "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": "2.6.37", "versionEndExcluding": "5.10.253" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.37", "versionEndExcluding": "5.15.203" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.37", "versionEndExcluding": "6.1.167" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.37", "versionEndExcluding": "6.6.130" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.37", "versionEndExcluding": "6.12.78" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.37", "versionEndExcluding": "6.18.20" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.37", "versionEndExcluding": "6.19.10" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.37", "versionEndExcluding": "7.0" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/4eb245ff0d33b618e097a2c23de5df56d4ad6969" }, { "url": "https://git.kernel.org/stable/c/3ee5b9e3de4b8bdd74183d83205481c91a9effc8" }, { "url": "https://git.kernel.org/stable/c/87a803edb2ded911cb587c53bff179d2a2ed2a28" }, { "url": "https://git.kernel.org/stable/c/1879319d790f7d57622cdc22807b60ea78b56b6d" }, { "url": "https://git.kernel.org/stable/c/78432d8f0372c71c518096395537fa12be7ff24e" }, { "url": "https://git.kernel.org/stable/c/389bae9a4409934e8b8d4dbdaaf02a3ae71cf8e4" }, { "url": "https://git.kernel.org/stable/c/cbede2e833da1893afbea9b3ff29b5dda23a4a91" }, { "url": "https://git.kernel.org/stable/c/453b8fb68f3641fea970db88b7d9a153ed2a37e8" } ], "title": "xen/privcmd: restrict usage in unprivileged domU", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "title": "CVE Program Container", "references": [ { "url": "http://xenbits.xen.org/xsa/advisory-482.html" }, { "url": "http://www.openwall.com/lists/oss-security/2026/03/24/2" }, { "url": "http://www.openwall.com/lists/oss-security/2026/03/24/3" }, { "url": "http://www.openwall.com/lists/oss-security/2026/03/24/4" }, { "url": "http://www.openwall.com/lists/oss-security/2026/03/24/5" }, { "url": "http://www.openwall.com/lists/oss-security/2026/03/26/4" } ], "providerMetadata": { "orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2026-03-26T16:26:26.454Z" } } ] } }