CVE-2020-21686 Explained : Impact and Mitigation

A stack-use-after-scope issue in NASM before version 2.15.04 can lead to a denial of service attack through a crafted asm file.

Understanding CVE-2020-21686

What is CVE-2020-21686?

The CVE-2020-21686 vulnerability is a stack-use-after-scope issue found in the expand_mmac_params function in preproc.c in NASM before version 2.15.04. This vulnerability can be exploited by remote attackers to cause a denial of service by using a specially crafted asm file.

The Impact of CVE-2020-21686

This vulnerability can result in a denial of service attack, potentially disrupting the normal operation of the affected system.

Technical Details of CVE-2020-21686

Vulnerability Description

The issue arises from improper handling of memory after it has gone out of scope, leading to potential exploitation by attackers.

Affected Systems and Versions

Vendor: n/a
Product: n/a
Versions: All versions before 2.15.04 are affected

Exploitation Mechanism

Attackers can exploit this vulnerability by creating a specially crafted asm file to trigger the stack-use-after-scope issue, causing a denial of service.

Mitigation and Prevention

Immediate Steps to Take

Update NASM to version 2.15.04 or later to mitigate the vulnerability
Monitor network traffic for any signs of exploitation

Long-Term Security Practices

Regularly update software and apply patches promptly
Implement network segmentation to limit the impact of potential attacks

Patching and Updates

Apply the latest patches and updates provided by NASM to address the vulnerability