CVE-2021-46993

Local kernel corruption via miscomputed util-clamp index

Published Feb 28, 2024 · Updated Aug 5, 2026

Out-of-bounds access in Linux kernel util-clamp scheduling allows local users to corrupt kernel memory through crafted clamp values. The uclamp bucket calculation divides the maximum clamp value by a rounded-down bucket size without capping the resulting index, so 1024 can select bucket 20 in a 20-entry array. An unprivileged same-owner process can reach the flaw through sched_setattr, causing adjacent scheduler-state reads and writes that can disclose data, corrupt execution, or hang the host.

CVSS severity7.8
High
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds access in Linux kernel util-clamp scheduling allows local users to corrupt kernel memory through crafted clamp values. The uclamp bucket calculation divides the maximum clamp value by a rounded-down bucket size without capping the resulting index, so 1024 can select bucket 20 in a 20-entry array. An unprivileged same-owner process can reach the flaw through sched_setattr, causing adjacent scheduler-state reads and writes that can disclose data, corrupt execution, or hang the host.

The record

CVE
CVE-2021-46993
Published
Feb 28, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-125, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 28, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.3
  2. Affected versionversion=69842cba9ace84849bb9b8edcdf2cefccd97901c <3da3f804b82a0a382d523a21acf4cf3bb35f936d
  3. Affected versionversion=69842cba9ace84849bb9b8edcdf2cefccd97901c <42ee47c7e3569d9a0e2cb5053c496d97d380472f
  4. Affected versionversion=69842cba9ace84849bb9b8edcdf2cefccd97901c <687f523c134b7f0bd040ee1230f6d17990d54172
  5. Affected versionversion=69842cba9ace84849bb9b8edcdf2cefccd97901c <6d2f8909a5fabb73fe2a63918117943986c39b6c
  6. Affected versionversion=69842cba9ace84849bb9b8edcdf2cefccd97901c <f7347c85490b92dd144fa1fba9e1eca501656ab3

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.3; version=69842cba9ace84849bb9b8edcdf2cefccd97901c <3da3f804b82a0a382d523a21acf4cf3bb35f936d; version=69842cba9ace84849bb9b8edcdf2cefccd97901c <42ee47c7e3569d9a0e2cb5053c496d97d380472f; version=69842cba9ace84849bb9b8edcdf2cefccd97901c <687f523c134b7f0bd040ee1230f6d17990d54172; version=69842cba9ace84849bb9b8edcdf2cefccd97901c <6d2f8909a5fabb73fe2a63918117943986c39b6c; version=69842cba9ace84849bb9b8edcdf2cefccd97901c <f7347c85490b92dd144fa1fba9e1eca501656ab3

Published CVSS scores

7.8kernel.orgCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.1NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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