Executive brief
Kamailio is an open-source SIP server used to route voice and video calls in telecom networks. A flaw in the IMS P-CSCF module allows a remote attacker to crash the service by sending concurrent registration and de-registration requests, causing a memory corruption issue that terminates worker processes. This disrupts call processing for affected users.
Technical details
The vulnerability is a double-free memory corruption bug in the ims_registrar_pcscf module, specifically in the sec_agree.c:parse_sec_agree() function that handles security-agreement parsing. The flaw occurs when concurrent REGISTER and de-REGISTER requests for the same contact are processed simultaneously; one execution path continues handling security-agreement state while another updates or expires the pending registration, leading to inconsistent internal state and a double memory free. The attack requires network access to the SIP server and no authentication is needed—an unauthenticated attacker can send overlapping registration requests with varying expiry times to trigger a crash. The issue has been fixed in the Kamailio repository (commit 722c06b) by preventing the double free condition.
Affected products
- Kamailio Kamailio 6.1.1 and before
Timeline
- 2026-09-01: disclosed
- 2026-09-01: patched: Fix available in commit 722c06b