{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2021-46993", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-02-27T18:42:55.949Z", "datePublished": "2024-02-28T08:13:18.494Z", "dateUpdated": "2026-08-05T08:45:26.827Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T08:45:26.827Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsched: Fix out-of-bound access in uclamp\n\nUtil-clamp places tasks in different buckets based on their clamp values\nfor performance reasons. However, the size of buckets is currently\ncomputed using a rounding division, which can lead to an off-by-one\nerror in some configurations.\n\nFor instance, with 20 buckets, the bucket size will be 1024/20=51. A\ntask with a clamp of 1024 will be mapped to bucket id 1024/51=20. Sadly,\ncorrect indexes are in range [0,19], hence leading to an out of bound\nmemory access.\n\nClamp the bucket id to fix the issue." } ], "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 bug is reached via the local sched_setattr syscall when a task sets util-clamp attributes; it is not reachable from the network stack or remote protocol handlers.\nAC:L - On the primary uclamp deployment (Android GKI with UCLAMP_BUCKETS_COUNT=20), setting clamp value 1024 reliably maps to out-of-range bucket_id 20 with no race or attacker-uncontrollable condition.\nPR:L - An unprivileged process can set its own sched_util_min/max through sched_setattr; __sched_setscheduler does not require CAP_SYS_NICE for UTIL_CLAMP on a same-owner fair-policy task.\nUI:N - Exploitation requires only the attacker’s own syscalls; no victim action such as opening a file or mounting a filesystem is needed.\nS:U - The corruption stays within the host kernel’s scheduling authority and does not cross a VM, IOMMU, or other security boundary.\nC:H - The out-of-bounds bucket access reads and writes adjacent per-CPU runqueue memory (including into cfs_rq), which can be leveraged for kernel information disclosure under the memory-corruption guidance.\nI:H - uclamp_rq_inc_id/dec_id perform out-of-bounds writes (tasks++/value assignment) that, for UCLAMP_MAX, land on uclamp_flags and the start of cfs_rq, enabling scheduler-state corruption and control-flow impact.\nA:H - Corrupting runqueue uclamp/cfs state can cause kernel warnings, oopses, or hangs, as seen when the bug was found via SCHED_WARN_ON on Android." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "kernel/sched/core.c" ], "versions": [ { "version": "69842cba9ace84849bb9b8edcdf2cefccd97901c", "lessThan": "687f523c134b7f0bd040ee1230f6d17990d54172", "status": "affected", "versionType": "git" }, { "version": "69842cba9ace84849bb9b8edcdf2cefccd97901c", "lessThan": "f7347c85490b92dd144fa1fba9e1eca501656ab3", "status": "affected", "versionType": "git" }, { "version": "69842cba9ace84849bb9b8edcdf2cefccd97901c", "lessThan": "3da3f804b82a0a382d523a21acf4cf3bb35f936d", "status": "affected", "versionType": "git" }, { "version": "69842cba9ace84849bb9b8edcdf2cefccd97901c", "lessThan": "42ee47c7e3569d9a0e2cb5053c496d97d380472f", "status": "affected", "versionType": "git" }, { "version": "69842cba9ace84849bb9b8edcdf2cefccd97901c", "lessThan": "6d2f8909a5fabb73fe2a63918117943986c39b6c", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "kernel/sched/core.c" ], "versions": [ { "version": "5.3", "status": "affected" }, { "version": "0", "lessThan": "5.3", "status": "unaffected", "versionType": "semver" }, { "version": "5.4.120", "lessThanOrEqual": "5.4.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.38", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.11.22", "lessThanOrEqual": "5.11.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.12.5", "lessThanOrEqual": "5.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.13", "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": "5.3", "versionEndExcluding": "5.4.120" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", 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