What is CVE-2021-3489?

CVE-2021-3489 is a high-severity vulnerability in Linux Kernel, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 7.8/10. Published 2021-06-04.

How severe is CVE-2021-3489?

High severity. CVSS v3 base score is 7.8 out of 10.

Is CVE-2021-3489 known to be exploited?

4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Buffer overflow in Linux Kernel

CVE-2021-3489

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).

Vulnerability class: Buffer Overflow

Published 2021-06-04 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.8 (High). Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.005 (44.8th percentile), scored 2026-10-19.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 45th percentile — 44.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000

Affected products

Linux Kernel — versions trunk, linux-5.12.y, linux-5.11.y
Linux Kernel — versions 5.13
Canonical Ubuntu Linux — versions 20.04, 20.10, 21.04

Weakness classification (CWE)

Public proof-of-concept exploits

References

www.openwall.com/lists/oss-security/2021/05/11/10 (mailing-list, Mailing List, Third Party Advisory)
git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/ (Patch, Vendor Advisory)
www.zerodayinitiative.com/advisories/ZDI-21-590/ (VDB Entry, Third Party Advisory)
ubuntu.com/security/notices/USN-4950-1 (vendor-advisory, Third Party Advisory)
ubuntu.com/security/notices/USN-4949-1 (vendor-advisory, Third Party Advisory)
security.netapp.com/advisory/ntap-20210716-0004/ (Third Party Advisory)

Frequently asked questions

What is CVE-2021-3489?: CVE-2021-3489 is a high-severity vulnerability in Linux Kernel, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 7.8/10. Published 2021-06-04.
How severe is CVE-2021-3489?: High severity. CVSS v3 base score is 7.8 out of 10.
Is CVE-2021-3489 known to be exploited?: 4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.