CVE-2021-3489: Canonical Ubuntu Linux

High severity, CVSS 7.8. EPSS: 0.6% chance of exploitation in the next 30 days.

The eBPF RINGBUF bpf_ringbuf_reserve() function in the Linux kernel did not check that the allocated size was smaller than the ringbuf size, allowing an attacker to perform out-of-bounds writes within the kernel and therefore, arbitrary code execution. This issue was fixed via commit 4b81ccebaeee ("bpf, ringbuf: Deny reserve of buffers larger than ringbuf") (v5.13-rc4) and backported to the stable kernels in v5.12.4, v5.11.21, and v5.10.37. It was introduced via 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it") (v5.8-rc1).

Affected products

• Canonical Ubuntu Linux: version 20.04 only; version 20.10 only; version 21.04 only
• Linux Linux Kernel: from 5.8, before 5.10.37 (fixed in 5.10.37); from 5.11, before 5.11.21 (fixed in 5.11.21); from 5.12, before 5.12.4 (fixed in 5.12.4); version 5.13 only

Published 2021-06-04. Last modified 2026-06-17.