CVE-2021-3939 : Exploit Details and Defense Strategies

Ubuntu-specific modifications to accountsservice led to a vulnerability where the fallback_locale variable, pointing to static storage, was freed. This issue affected versions 0.6.55-0ubuntu12~20.04, 0.6.55-0ubuntu13, and 0.6.55-0ubuntu14.

Understanding CVE-2021-3939

This CVE pertains to a memory corruption vulnerability in accountsservice due to the freeing of static storage, allowing for potential code execution.

What is CVE-2021-3939?

CVE-2021-3939 is a vulnerability in accountsservice caused by certain Ubuntu-specific modifications, leading to memory corruption.

The Impact of CVE-2021-3939

The vulnerability could be exploited by an attacker to execute arbitrary code or trigger a denial of service (DoS) condition on affected systems.

Technical Details of CVE-2021-3939

The following technical details provide insight into the vulnerability.

Vulnerability Description

A flaw in the user_change_language_authorized_cb function allowed the freeing of the fallback_locale variable pointing to static storage, creating a memory corruption issue.

Affected Systems and Versions

Versions 0.6.55-0ubuntu12~20.04, 0.6.55-0ubuntu13, and 0.6.55-0ubuntu14 were affected by this CVE.

Exploitation Mechanism

The vulnerability could be exploited via the SetLanguage dbus function, potentially leading to arbitrary code execution or a DoS.

Mitigation and Prevention

To address and prevent exploitation of CVE-2021-3939, consider the following steps:

Immediate Steps to Take

Apply the necessary patches provided by Ubuntu for the affected versions.
Monitor for any unusual activities on the system that could indicate exploitation.

Long-Term Security Practices

Regularly update software and systems to ensure the latest security patches are in place.
Implement proper access controls and configurations to limit the impact of potential vulnerabilities.

Patching and Updates

Ensure that patches provided by Ubuntu for accountsservice versions 0.6.55-0ubuntu12~20.04.5, 0.6.55-0ubuntu13.3, and 0.6.55-0ubuntu14.1 are applied promptly to safeguard the system.