CVE-2021-41157 : Vulnerability Insights and Analysis

FreeSWITCH is a Software Defined Telecom Stack enabling the digital transformation from proprietary telecom switches to a software implementation that runs on any commodity hardware. This CVE relates to a security issue where SIP requests of the type SUBSCRIBE are not authenticated in certain versions of FreeSWITCH, potentially exposing systems to abuse and privacy concerns.

Understanding CVE-2021-41157

This vulnerability allows attackers to subscribe to user agent event notifications without authentication, posing risks of privacy breaches and social engineering attacks.

What is CVE-2021-41157?

In FreeSWITCH versions prior to 1.10.6, SIP SUBSCRIBE messages are not authenticated by default, leaving systems vulnerable to unauthorized subscription requests.

The Impact of CVE-2021-41157

Attackers can monitor the status of target SIP extensions without authentication, posing privacy risks and enabling potential social engineering attacks.

Technical Details of CVE-2021-41157

In-depth technical information about the vulnerability and affected systems.

Vulnerability Description

SIP SUBSCRIBE requests are not authenticated in FreeSWITCH versions earlier than 1.10.6, allowing unauthorized access to subscribe to user agent event notifications.

Affected Systems and Versions

Product: FreeSWITCH
Vendor: SignalWire
Versions Affected: < 1.10.6

Exploitation Mechanism

Attackers can abuse the lack of authentication in SIP SUBSCRIBE messages to subscribe to user agent event notifications without legitimate access.

Mitigation and Prevention

Actions to mitigate and prevent exploitation of CVE-2021-41157.

Immediate Steps to Take

Upgrade FreeSWITCH to version 1.10.6 or newer to address the vulnerability.
Ensure configuration is updated after upgrading to the fixed version.
Authenticate SIP SUBSCRIBE messages by default or set the

auth-subscriptions

parameter.

Long-Term Security Practices

Regularly update FreeSWITCH and review security configurations.
Implement network segmentation to limit the impact of potential unauthorized access.

Patching and Updates

Apply patches and updates provided by SignalWire promptly to stay protected from known vulnerabilities.