CVE-2021-4090 : What You Need to Know

An out-of-bounds (OOB) memory write flaw was found in the NFSD in the Linux kernel, specifically in nfsd4_decode_bitmap4 in fs/nfsd/nfs4xdr.c. This vulnerability may allow a local attacker with user privilege to gain access to out-of-bounds memory, posing a threat to system integrity and confidentiality.

Understanding CVE-2021-4090

This section delves into the details of the CVE-2021-4090 vulnerability.

What is CVE-2021-4090?

CVE-2021-4090 is an out-of-bounds (OOB) memory write flaw discovered in the NFSD in the Linux kernel. This flaw could allow a local attacker with user privilege to access out-of-bounds memory.

The Impact of CVE-2021-4090

The impact of this vulnerability lies in the potential compromise of system integrity and confidentiality due to unauthorized access to memory beyond the intended limits.

Technical Details of CVE-2021-4090

In this section, the technical aspects of CVE-2021-4090 are explored.

Vulnerability Description

The vulnerability arises from a missing sanity check in the NFSD, which could result in a write beyond bmval[bmlen-1] in nfsd4_decode_bitmap4.

Affected Systems and Versions

The affected system is the 'kernel' with version 'kernel 5.16 rc2'.

Exploitation Mechanism

A local attacker with user privilege can exploit this vulnerability to gain access to out-of-bounds memory in the NFSD in the Linux kernel.

Mitigation and Prevention

Here we discuss the steps to mitigate and prevent the CVE-2021-4090 vulnerability.

Immediate Steps to Take

Users are advised to apply relevant patches and updates provided by the Linux kernel maintainers promptly.

Long-Term Security Practices

Implementing the principle of least privilege and regular security updates can help prevent similar vulnerabilities in the future.

Patching and Updates

Regularly monitor security advisories from the Linux kernel community and apply patches as soon as they are released.