CVE-2023-51443: FreeSWITCH susceptible to Denial of Service via DTLS Hello packets during call initiation

Vulnerability summary

CVE-2023-51443 is a high (CVSS 7.5) vulnerability in freeswitch. EPSS estimates a 1.49% chance of exploitation in the next 30 days, higher than 74.2% of scored vulnerabilities. 2 public exploits are recorded.

Timeline

1. 27-12-2023
   PublishedVulnerability first disclosed.
2. 04-11-2025
   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. Prior to version 1.10.11, when handling DTLS-SRTP for media setup, FreeSWITCH is susceptible to Denial of Service due to a race condition in the hello handshake phase of the DTLS protocol. This attack can be done continuously, thus denying new DTLS-SRTP encrypted calls during the attack. If an attacker manages to send a ClientHello DTLS message with an invalid CipherSuite (such as `TLS_NULL_WITH_NULL_NULL`) to the port on the FreeSWITCH server that is expecting packets from the caller, a DTLS error is generated. This results in the media session being torn down, which is followed by teardown at signaling (SIP) level too. Abuse of this vulnerability may lead to a massive Denial of Service on vulnerable FreeSWITCH servers for calls that rely on DTLS-SRTP. To address this vulnerability, upgrade FreeSWITCH to 1.10.11 which includes the security fix. The solution implemented is to drop all packets from addresses that have not been validated by an ICE check.

• CWE-703Improper Check or Handling of Exceptional ConditionsThe product does not properly anticipate or handle exceptional conditions that rarely occur during normal operation of the product.