CVE-2021-4159

Severity: medium (CVSS 4.4 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: 2022-08-24 · updated 2026-06-17
Weakness: CWE-202

Description

A vulnerability was found in the Linux kernel's EBPF verifier when handling internal data structures. Internal memory locations could be returned to userspace. A local attacker with the permissions to insert eBPF code to the kernel can use this to leak internal kernel memory details defeating some of the exploit mitigations in place for the kernel.

Affected products

Debian Linux: 10.0
Linux kernel: before 5.7 — fixed in 5.7
Red Hat Enterprise Linux: 8.0

How to fix

Upgrade to a fixed version: Linux kernel 5.7. Check the vendor advisory for mitigations.

References

https://access.redhat.com/security/cve/CVE-2021-4159
https://bugzilla.redhat.com/show_bug.cgi?id=2036024
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=294f2fc6da27620a506e6c050241655459ccd6bd
https://lists.debian.org/debian-lts-announce/2022/10/msg00000.html
https://security-tracker.debian.org/tracker/CVE-2021-4159
https://access.redhat.com/security/cve/CVE-2021-4159
https://bugzilla.redhat.com/show_bug.cgi?id=2036024
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=294f2fc6da27620a506e6c050241655459ccd6bd
https://lists.debian.org/debian-lts-announce/2022/10/msg00000.html
https://security-tracker.debian.org/tracker/CVE-2021-4159

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