CVE-2021-38166

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-08-07 · updated 2026-10-08
Weakness: CWE-190

Description

In kernel/bpf/hashtab.c in the Linux kernel through 5.13.8, there is an integer overflow and out-of-bounds write when many elements are placed in a single bucket. NOTE: exploitation might be impractical without the CAP_SYS_ADMIN capability.

Affected products

Debian Linux: 11.0
Fedoraproject Fedora: 33, 34
Linux kernel: from 5.6 before 5.10.60; from 5.11 before 5.13.12 — fixed in 5.10.60, 5.13.12

How to fix

Upgrade to a fixed version: Linux kernel 5.10.60, 5.13.12. Check the vendor advisory for mitigations.

References

https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=c4eb1f403243fc7bbb7de644db8587c03de36da6
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GUVLBJKZMWA3E3YXSH4SZ7BOYGJP4GXP/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UL6CH5M5PRLMA3KPBX4LPUO6Z73GRISO/
https://lore.kernel.org/bpf/20210806150419.109658-1-th.yasumatsu%40gmail.com/
https://security.netapp.com/advisory/ntap-20210909-0001/
https://www.debian.org/security/2021/dsa-4978
https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=c4eb1f403243fc7bbb7de644db8587c03de36da6
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GUVLBJKZMWA3E3YXSH4SZ7BOYGJP4GXP/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UL6CH5M5PRLMA3KPBX4LPUO6Z73GRISO/
https://lore.kernel.org/bpf/20210806150419.109658-1-th.yasumatsu%40gmail.com/
https://security.netapp.com/advisory/ntap-20210909-0001/
https://www.debian.org/security/2021/dsa-4978

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