CVE-2020-16126 Explained : Impact and Mitigation

An Ubuntu-specific modification to AccountsService in versions before 0.6.55-0ubuntu13.2, among other earlier versions, improperly dropped the ruid, allowing untrusted users to send signals to AccountService, thus stopping it from handling D-Bus messages in a timely fashion.

Understanding CVE-2020-16126

This CVE involves a vulnerability in the AccountsService software affecting specific versions.

What is CVE-2020-16126?

CVE-2020-16126 is a vulnerability in AccountsService versions prior to 0.6.55-0ubuntu13.2, which allows unprivileged users to send signals to the service, disrupting its message handling.

The Impact of CVE-2020-16126

The vulnerability poses a low severity risk with a CVSS base score of 3.3. It affects the availability of the service but does not impact confidentiality or integrity.

Technical Details of CVE-2020-16126

This section covers the technical aspects of the CVE.

Vulnerability Description

The issue arises from the improper dropping of the ruid in affected versions, enabling untrusted users to interfere with AccountService's signal processing.

Affected Systems and Versions

Product: accountsservice
Vendor: Freedesktop
Versions:
0.6.35-0ubuntu7.3
0.6.40-2ubuntu11
0.6.45-1ubuntu1
0.6.55-0ubuntu12~20.04.4
0.6.55-0ubuntu13

Exploitation Mechanism

The vulnerability allows unprivileged users to disrupt the service by sending signals, impacting its ability to handle D-Bus messages efficiently.

Mitigation and Prevention

Protective measures to address CVE-2020-16126.

Immediate Steps to Take

Update AccountsService to a non-vulnerable version.
Monitor system logs for any suspicious activity.
Restrict access to the affected service.

Long-Term Security Practices

Regularly update software and apply security patches.
Implement the principle of least privilege to limit user capabilities.

Patching and Updates

Apply the latest patches provided by the vendor to fix the vulnerability.