CVE-2019-20398 : Security Advisory and Response

CVE-2019-20398 is a vulnerability in libyang that can lead to a NULL pointer dereference, potentially causing crashes in applications using libyang to analyze yang files with untrusted input.

Understanding CVE-2019-20398

What is CVE-2019-20398?

The vulnerability lies in the function lys_extension_instances_free() in libyang before v1.0-r3 due to a duplication of unresolved extensions in the function lys_restr_dup().

The Impact of CVE-2019-20398

The issue can result in a NULL pointer dereference, leading to crashes in applications that process yang files with untrusted content.

Technical Details of CVE-2019-20398

Vulnerability Description

The vulnerability in libyang before v1.0-r3 allows for a NULL pointer dereference, posing a risk of application crashes.

Affected Systems and Versions

Vendor: n/a
Product: n/a
Versions: All versions are affected.

Exploitation Mechanism

Exploiting this vulnerability requires crafting yang files with malicious content to trigger the NULL pointer dereference.

Mitigation and Prevention

Immediate Steps to Take

Update libyang to version v1.0-r3 or later to mitigate the vulnerability.
Avoid processing yang files from untrusted sources until the patch is applied.

Long-Term Security Practices

Regularly update software libraries and dependencies to address known vulnerabilities.
Implement input validation mechanisms to prevent the processing of malicious content.

Patching and Updates

Apply the security update provided by libyang to address the vulnerability and prevent potential crashes.