A stack-based buffer overflow in the OpenSIPS sip_to_json() function allows unauthenticated attackers to trigger a process crash or potentially execute arbitrary code via a crafted SIP packet.

The vulnerability occurs when the sip_to_json() function copies SIP header names into a fixed 255-byte stack buffer without bounds checking. An unauthenticated attacker can send a crafted SIP message with an oversized header to the SIP port, triggering a buffer overflow that can overwrite the return address.

A CVSS score of 9.8 indicates a critical risk, as this vulnerability allows for remote exploitation without authentication. Successful exploitation can lead to total system compromise or service disruption, which is particularly damaging for critical SIP infrastructure and telecommunications services.

Immediate Action: Check the official OpenSIPS security advisory for the latest patch or guidance on how to disable the vulnerable sip_to_json() functionality in routing scripts.

Proactive Monitoring: Monitor SIP traffic for malformed packets or abnormally long header strings that may indicate an exploitation attempt.

Compensating Controls: Utilize an Intrusion Prevention System (IPS) to filter and drop SIP packets that contain headers exceeding standard length specifications.

Public Exploit Available: No (exploit_available: false)

Given that no fix was available at the time of publication, administrators should immediately review their routing scripts to determine if sip_to_json() is in use. If it is, consider disabling the function or implementing strict packet inspection at the perimeter until a verified security patch is applied.