{"id":"CVE-2021-46993","state":"PUBLISHED","title":"sched: Fix out-of-bound access in uclamp","description":"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.","publishedAt":"2024-02-28T08:13:18.494Z","updatedAt":"2026-08-05T08:45:26.827Z","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":"69842cba9ace84849bb9b8edcdf2cefccd97901c","status":"affected","lessThan":"687f523c134b7f0bd040ee1230f6d17990d54172","versionType":"git"},{"version":"69842cba9ace84849bb9b8edcdf2cefccd97901c","status":"affected","lessThan":"f7347c85490b92dd144fa1fba9e1eca501656ab3","versionType":"git"},{"version":"69842cba9ace84849bb9b8edcdf2cefccd97901c","status":"affected","lessThan":"3da3f804b82a0a382d523a21acf4cf3bb35f936d","versionType":"git"},{"version":"69842cba9ace84849bb9b8edcdf2cefccd97901c","status":"affected","lessThan":"42ee47c7e3569d9a0e2cb5053c496d97d380472f","versionType":"git"},{"version":"69842cba9ace84849bb9b8edcdf2cefccd97901c","status":"affected","lessThan":"6d2f8909a5fabb73fe2a63918117943986c39b6c","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sched/core.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.3","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.3","versionType":"semver"},{"version":"5.4.120","status":"unaffected","lessThanOrEqual":"5.4.*","versionType":"semver"},{"version":"5.10.38","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.11.22","status":"unaffected","lessThanOrEqual":"5.11.*","versionType":"semver"},{"version":"5.12.5","status":"unaffected","lessThanOrEqual":"5.12.*","versionType":"semver"},{"version":"5.13","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sched/core.c"]}],"references":["https://git.kernel.org/stable/c/687f523c134b7f0bd040ee1230f6d17990d54172","https://git.kernel.org/stable/c/f7347c85490b92dd144fa1fba9e1eca501656ab3","https://git.kernel.org/stable/c/3da3f804b82a0a382d523a21acf4cf3bb35f936d","https://git.kernel.org/stable/c/42ee47c7e3569d9a0e2cb5053c496d97d380472f","https://git.kernel.org/stable/c/6d2f8909a5fabb73fe2a63918117943986c39b6c"],"weaknesses":[],"ingestedAt":"2026-10-29T19:49:16.371Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2021/46xxx/CVE-2021-46993.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2021-46993","state":"PUBLISHED","datePublished":"2024-02-28T08:13:18.494Z","dateUpdated":"2026-08-05T08:45:26.827Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2024-02-27T18:42:55.949Z"},"containers":{"cna":{"title":"sched: Fix out-of-bound access in uclamp","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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"69842cba9ace84849bb9b8edcdf2cefccd97901c","status":"affected","lessThan":"687f523c134b7f0bd040ee1230f6d17990d54172","versionType":"git"},{"version":"69842cba9ace84849bb9b8edcdf2cefccd97901c","status":"affected","lessThan":"f7347c85490b92dd144fa1fba9e1eca501656ab3","versionType":"git"},{"version":"69842cba9ace84849bb9b8edcdf2cefccd97901c","status":"affected","lessThan":"3da3f804b82a0a382d523a21acf4cf3bb35f936d","versionType":"git"},{"version":"69842cba9ace84849bb9b8edcdf2cefccd97901c","status":"affected","lessThan":"42ee47c7e3569d9a0e2cb5053c496d97d380472f","versionType":"git"},{"version":"69842cba9ace84849bb9b8edcdf2cefccd97901c","status":"affected","lessThan":"6d2f8909a5fabb73fe2a63918117943986c39b6c","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sched/core.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.3","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.3","versionType":"semver"},{"version":"5.4.120","status":"unaffected","lessThanOrEqual":"5.4.*","versionType":"semver"},{"version":"5.10.38","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.11.22","status":"unaffected","lessThanOrEqual":"5.11.*","versionType":"semver"},{"version":"5.12.5","status":"unaffected","lessThanOrEqual":"5.12.*","versionType":"semver"},{"version":"5.13","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sched/core.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/687f523c134b7f0bd040ee1230f6d17990d54172"},{"url":"https://git.kernel.org/stable/c/f7347c85490b92dd144fa1fba9e1eca501656ab3"},{"url":"https://git.kernel.org/stable/c/3da3f804b82a0a382d523a21acf4cf3bb35f936d"},{"url":"https://git.kernel.org/stable/c/42ee47c7e3569d9a0e2cb5053c496d97d380472f"},{"url":"https://git.kernel.org/stable/c/6d2f8909a5fabb73fe2a63918117943986c39b6c"}],"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."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T08:45:26.827Z"},"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:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"5.10.38"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"5.11.22"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"5.12.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"5.13"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CVE Program Container","references":[{"url":"https://git.kernel.org/stable/c/687f523c134b7f0bd040ee1230f6d17990d54172","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/f7347c85490b92dd144fa1fba9e1eca501656ab3","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/3da3f804b82a0a382d523a21acf4cf3bb35f936d","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/42ee47c7e3569d9a0e2cb5053c496d97d380472f","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/6d2f8909a5fabb73fe2a63918117943986c39b6c","tags":["x_transferred"]}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2024-08-04T05:24:37.912Z"}},{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2021-46993","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2024-09-10T16:01:01.662746Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2024-09-11T17:33:38.812Z"}}]}}}