CVE-2021-37624 FreeSWITCH does not authenticate SIP MESSAGE requests, leading to spam and message spoofing
Attackers can send unauthenticated SIP messages to registered users, enabling spam and spoofing, unless authentication is explicitly enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-37624?
CVE-2021-37624 is a high-severity missing authorization vulnerability in signalwire freeswitch, published on 25 Oct 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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. Prior to version 1.10.7, FreeSWITCH does not authenticate SIP MESSAGE requests, leading to spam and message spoofing. By default, SIP requests of the type MESSAGE (RFC 3428) are not authenticated in the affected versions of FreeSWITCH. MESSAGE requests are relayed to SIP user agents registered with the FreeSWITCH server without requiring any authentication. Although this behaviour can be changed by setting the `auth-messages` parameter to `true`, it is not the default setting. Abuse of this security issue allows attackers to send SIP MESSAGE messages to any SIP user agent that is registered with the server without requiring authentication. Additionally, since no authentication is required, chat messages can be spoofed to appear to come from trusted entities. Therefore, abuse can lead to spam and enable social engineering, phishing and similar attacks. This issue is patched in version 1.10.7. Maintainers recommend that this SIP message type is authenticated by default so that FreeSWITCH administrators do not need to be explicitly set the `auth-messages` parameter. When following such a recommendation, a new parameter can be introduced to explicitly disable authentication.
Which versions are affected by CVE-2021-37624?
It affects 1 product.
Products include Freeswitch Freeswitch.
How do I fix CVE-2021-37624?
Upgrade to a fixed version.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2021-37624 being exploited?
There is no known exploitation of CVE-2021-37624 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Other vulnerabilities in signalwire freeswitch
- CVE-2026-49841 FreeSWITCH: Pre-authentication heap buffer overflow in `mod_verto` HTTP POST body read
- CVE-2019-19492 Hardcoded credentials in n/a
- CVE-2026-49840 FreeSWITCH: Pre-authentication heap buffer overflow in libesl `Content-Length` parsing
- CVE-2021-41145 FreeSWITCH susceptible to Denial of Service via SIP flooding
- CVE-2026-45771 Freeswitch Denial-of-Service in SIP PUBLISH Requests via XML Entity Expansion
Sources
Also known as ALPINE-CVE-2021-37624, GHSA-mjcm-q9h8-9xv3.