CVE-2021-41157: FreeSWITCH does not authenticate SIP SUBSCRIBE requests by default

Vulnerability summary

CVE-2021-41157 is a medium (CVSS 5.3) Improper Authentication vulnerability in freeswitch. EPSS estimates a 1.70% chance of exploitation in the next 30 days, higher than 77.3% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 26-10-2021
   PublishedVulnerability first disclosed.
2. 04-08-2024
   Last modifiedVulnerability information updated.

Description

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. By default, SIP requests of the type SUBSCRIBE are not authenticated in the affected versions of FreeSWITCH. Abuse of this security issue allows attackers to subscribe to user agent event notifications without the need to authenticate. This abuse poses privacy concerns and might lead to social engineering or similar attacks. For example, attackers may be able to monitor the status of target SIP extensions. Although this issue was fixed in version v1.10.6, installations upgraded to the fixed version of FreeSWITCH from an older version, may still be vulnerable if the configuration is not updated accordingly. Software upgrades do not update the configuration by default. SIP SUBSCRIBE messages should be authenticated by default so that FreeSWITCH administrators do not need to explicitly set the `auth-subscriptions` parameter. When following such a recommendation, a new parameter can be introduced to explicitly disable authentication.

• CWE-287Improper AuthenticationWhen an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
• CWE-306Missing Authentication for Critical FunctionalityThe product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.