CVE-2021-22915 : What You Need to Know

Nextcloud Server versions prior to 19.0.11, 20.0.10, and 21.0.2 are susceptible to brute force attacks due to a failure in considering IPv6 subnets for rate-limiting. Attackers could exploit this vulnerability to evade rate-limit controls such as Nextcloud's brute-force protection.

Understanding CVE-2021-22915

This section delves into the specifics of CVE-2021-22915.

What is CVE-2021-22915?

CVE-2021-22915 pertains to the vulnerability in Nextcloud Server that allows attackers to launch brute force attacks by circumventing rate-limiting mechanisms, potentially compromising system security.

The Impact of CVE-2021-22915

The impact of CVE-2021-22915 includes the risk of unauthorized access to systems and sensitive data, posing a threat to the confidentiality and integrity of information stored within Nextcloud Server.

Technical Details of CVE-2021-22915

This section outlines the technical aspects of CVE-2021-22915.

Vulnerability Description

The vulnerability in Nextcloud Server arises from the exclusion of IPv6 subnets in rate-limiting considerations, enabling attackers to perform brute force attacks and bypass existing security controls.

Affected Systems and Versions

Nextcloud Server versions before 19.0.11, 20.0.10, and 21.0.2 are affected by CVE-2021-22915, leaving them vulnerable to exploitation by malicious actors seeking unauthorized access.

Exploitation Mechanism

Attackers can exploit this vulnerability through brute force attacks, leveraging the lack of proper rate-limiting checks on IPv6 subnets to gain entry and compromise Nextcloud Server environments.

Mitigation and Prevention

This section focuses on strategies to mitigate and prevent the exploitation of CVE-2021-22915.

Immediate Steps to Take

Users are advised to update Nextcloud Server to versions 19.0.11, 20.0.10, or 21.0.2 to remediate the vulnerability and enhance security posture. Additionally, enforcing robust password policies and monitoring for unusual login activities can help thwart brute force attacks.

Long-Term Security Practices

Implementing network-level security measures, such as firewall rules and intrusion detection systems, can bolster defense against brute force attacks and other malicious activities targeting Nextcloud Server.

Patching and Updates

Regularly updating Nextcloud Server to the latest secure versions and staying informed about security advisories from trusted sources like Nextcloud and relevant vendors is crucial in safeguarding systems against emerging vulnerabilities.