CVE-2021-43610

Vulnerability

Belle-sip versions before 5.0.20 contain a crash vulnerability triggered by an invalid From header in an unauthenticated SIP message. Specifically, a request URI without a parameter (e.g., sip:user@host without a ; parameter) causes a null pointer dereference or similar crash. The issue is distinct from CVE-2021-33056. Affected versions: all prior to 5.0.20. [1][2]

Exploitation

An attacker can send a crafted SIP message with a malformed From header containing a request URI that lacks any parameters. No authentication is required; the message is processed by the SIP stack. The crash occurs during parsing of the From header. [1][2]

Impact

Successful exploitation causes a denial of service (DoS) by crashing the application (e.g., Linphone) that uses the vulnerable Belle-sip library. The crash is immediate upon receipt of the malicious message. No code execution or data disclosure is indicated. [1][2]

Mitigation

The fix was released in Belle-sip version 5.0.20, which includes a commit that addresses the crash by adding proper validation of the From header. Users should upgrade to 5.0.20 or later. No workaround is documented. [1][2]