CVE-2021-34813 : Security Advisory and Response
Matrix libolm before 3.2.3 vulnerability (CVE-2021-34813) allows a malicious Matrix server to crash a client and potentially execute remote code. Learn how to mitigate this security flaw.
A vulnerability in Matrix libolm before version 3.2.3 could allow a malicious Matrix homeserver to crash a client and potentially lead to remote code execution in certain build configurations.
Understanding CVE-2021-34813
This vulnerability in Matrix libolm affects the security of clients interacting with a Matrix homeserver.
What is CVE-2021-34813?
Matrix libolm before 3.2.3 has a stack-based buffer overflow in olm_pk_decrypt, enabling a malicious server to crash a client while attempting to retrieve an Olm encrypted room key backup. This may open the door to remote code execution in specific nonstandard build settings.
The Impact of CVE-2021-34813
The vulnerability allows attackers to disrupt client-server communications, potentially leading to a denial of service (DoS) condition. Moreover, in specific configurations, it may escalate to remote code execution, enabling adversaries to execute arbitrary code on the client's system.
Technical Details of CVE-2021-34813
This section elaborates on the technical aspects of the vulnerability in Matrix libolm.
Vulnerability Description
The flaw in olm_pk_decrypt can trigger a stack-based buffer overflow when processing Olm encrypted room key backups, resulting in a client crash.
Affected Systems and Versions
All versions of Matrix libolm before 3.2.3 are vulnerable to this issue. Users operating on these versions are at risk.
Exploitation Mechanism
A malicious Matrix homeserver can exploit this vulnerability by crafting a specially designed Olm encrypted room key backup and sending it to a client, causing the buffer overflow and subsequent crash.
Mitigation and Prevention
To safeguard systems from CVE-2021-34813, immediate action and long-term security practices are essential.
Immediate Steps to Take
It is crucial to update Matrix libolm to version 3.2.3 or above to mitigate the vulnerability. Additionally, users should monitor for any unusual server-client interactions.
Long-Term Security Practices
Regularly updating software and maintaining a robust security posture by configuring systems securely can help prevent similar vulnerabilities in the future.
Patching and Updates
Patching the affected systems promptly with the latest security updates from Matrix.org is essential to eliminate the risk posed by CVE-2021-34813.