CVE-2021-3489 : Exploit Details and Defense Strategies

The eBPF RINGBUF bpf_ringbuf_reserve() function in the Linux kernel allowed out-of-bounds writes, leading to arbitrary code execution. This vulnerability affects Linux kernel versions less than v5.13-rc4, v5.12.4, v5.11.21, v5.10.37, and v5.8.

Understanding CVE-2021-3489

This CVE pertains to a vulnerability in the eBPF RINGBUF functionality in the Linux kernel that could be exploited for arbitrary code execution through out-of-bounds writes.

What is CVE-2021-3489?

The eBPF RINGBUF bpf_ringbuf_reserve() function lacked size validation, allowing attackers to write beyond the allocated memory and execute arbitrary code in the kernel.

The Impact of CVE-2021-3489

With a CVSS base score of 7.8 (High), this vulnerability has a significant impact by enabling attackers to execute arbitrary code within affected kernels with a local attack vector.

Technical Details of CVE-2021-3489

The vulnerability was introduced in Linux kernel v5.8-rc1 via a specific commit and was patched in subsequent versions to prevent out-of-bounds writes.

Vulnerability Description

The flaw in the eBPF RINGBUF functionality allowed attackers to write outside the allocated memory boundaries, potentially leading to arbitrary code execution within the kernel.

Affected Systems and Versions

Linux kernel versions less than v5.13-rc4, v5.12.4, v5.11.21, v5.10.37, and v5.8 are susceptible to this vulnerability.

Exploitation Mechanism

By exploiting the lack of size validation in the bpf_ringbuf_reserve() function, attackers could perform out-of-bounds writes, compromising the integrity and confidentiality of the affected systems.

Mitigation and Prevention

To mitigate the risks associated with CVE-2021-3489, immediate steps should be taken to address the vulnerability and prevent potential exploitation.

Immediate Steps to Take

Users are advised to apply the security patches provided by Linux maintainers to secure their systems against this vulnerability.

Long-Term Security Practices

Implementing robust security measures, performing regular system updates, and adhering to security best practices can help enhance the overall security posture and resilience of the system.

Patching and Updates

Ensure timely patching of the Linux kernel to versions v5.13-rc4, v5.12.4, v5.11.21, v5.10.37, or beyond to eliminate the vulnerability and protect systems from potential exploitation.