CVE-2021-46993: sched: Fix out-of-bound access in uclamp

Severity: high (CVSS 7.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-02-28 · updated 2026-08-04
Weakness: CWE-125

Description

In the Linux kernel, the following vulnerability has been resolved: sched: Fix out-of-bound access in uclamp Util-clamp places tasks in different buckets based on their clamp values for performance reasons. However, the size of buckets is currently computed using a rounding division, which can lead to an off-by-one error in some configurations. For instance, with 20 buckets, the bucket size will be 1024/20=51. A task with a clamp of 1024 will be mapped to bucket id 1024/51=20. Sadly, correct indexes are in range [0,19], hence leading to an out of bound memory access. Clamp the bucket id to fix the issue.

Affected products

Linux kernel: from 5.3 before 5.4.120; from 5.5 before 5.10.38; from 5.11 before 5.11.22; from 5.12 before 5.12.5 — fixed in 5.10.38, 5.11.22, 5.12.5, 5.4.120

How to fix

Upgrade to a fixed version: Linux kernel 5.10.38, 5.11.22, 5.12.5, 5.4.120. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2021-46993 or the next vulnerability affects your stack