What is CVE-2021-41157?

CVE-2021-41157 is a medium-severity vulnerability in Freeswitch, classified under Improper Authentication. CVSS score: 5.3/10. Published 2021-10-26.

How severe is CVE-2021-41157?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Is CVE-2021-41157 known to be exploited?

4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Auth bypass in Freeswitch

CVE-2021-41157

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.

Vulnerability class: Broken Authentication

EPSS: 0.017 (74.7th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.

Affected products

Freeswitch
Signalwire Freeswitch — versions < 1.10.6

Weakness classification (CWE)

Public proof-of-concept exploits

References

security-advisories@github.com (x_refsource_CONFIRM, Exploit, Third Party Advisory)
security-advisories@github.com (Patch, Third Party Advisory, x_refsource_MISC)
security-advisories@github.com (Third Party Advisory, x_refsource_MISC, Release Notes)
security-advisories@github.com (mailing-list, x_refsource_FULLDISC, Mailing List, Third Party Advisory)

Frequently asked questions

What is CVE-2021-41157?: CVE-2021-41157 is a medium-severity vulnerability in Freeswitch, classified under Improper Authentication. CVSS score: 5.3/10. Published 2021-10-26.
How severe is CVE-2021-41157?: Medium severity. CVSS v3 base score is 5.3 out of 10.
Is CVE-2021-41157 known to be exploited?: 4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.