CVE-2023-36811 Explained : Impact and Mitigation

A detailed analysis of the Archive Spoofing Vulnerability in Borgbackup.

Understanding CVE-2023-36811

In August 2023, a Medium severity Archive Spoofing Vulnerability, identified as CVE-2023-36811, was discovered in Borgbackup, affecting versions prior to 1.2.5.

What is CVE-2023-36811?

Borgbackup, an open-source archiver with encryption, had a cryptographic signature verification flaw. This flaw could allow an attacker to create fake archives, potentially leading to data loss in the backup repository. The attacker needed to insert files in backups without additional headers and gain write access to the repository.

The Impact of CVE-2023-36811

Exploiting this vulnerability did not expose plain text to attackers nor affect the authenticity of existing archives. While creating fake archives was challenging for large archives, it was possible for small ones. Fixing the issue required an update to version 1.2.5 of Borgbackup.

Technical Details of CVE-2023-36811

This section dives into the vulnerability specifics.

Vulnerability Description

The flaw in the cryptographic authentication scheme of Borgbackup enabled attackers to manipulate archives, potentially leading to backup data loss without revealing plaintext or compromising the integrity of existing archives.

Affected Systems and Versions

Borgbackup versions earlier than 1.2.5 were impacted by this vulnerability. Users of these versions were at risk of data loss due to potential archive spoofing.

Exploitation Mechanism

Attackers needed the capability to insert specific files into backups and gain write access to the repository to exploit this vulnerability and create fake archives.

Mitigation and Prevention

To safeguard systems from this vulnerability, certain steps need to be taken.

Immediate Steps to Take

Users are strongly advised to upgrade to Borgbackup version 1.2.5. Along with updating, users must follow the documented upgrade procedure to ensure the fix is properly implemented.

Long-Term Security Practices

Regularly reviewing archives for timestamp and content validity using tools like "borg check --repair" before pruning them can help prevent data loss after a potential attack.

Patching and Updates

The issue has been resolved in Borgbackup version 1.2.5. Users are urged to update to this version promptly to mitigate the risk of archive spoofing and data loss.