CVE-2026-45809: Opensips

High severity, CVSS 8.7. EPSS: 0.6% chance of exploitation in the next 30 days.

OpenSIPS is a Session Initiation Protocol (SIP) server implementation. Versions prior to 3.6.6 and 4.0.0-rc1 contain a denial of service vulnerability in the watcherinfo generation functionality. An attacker can create an oversized watcher entry by sending a SUBSCRIBE Event: presence request with a long From URI, and then trigger presence.winfo watcherinfo XML generation for the same presentity. OpenSIPS copies the stored watcher URI into a fixed-size stack buffer, overflowing it and crashing the process. A remote attacker can crash an OpenSIPS worker in deployments that expose handle_subscribe() and allow watcherinfo (presence.winfo) generation. The issue is configuration-dependent because the presence and presence_xml modules must be loaded and SUBSCRIBE routing must be reachable. This issue has been fixed in versions 3.6.6 and 4.0.0-rc1.

Affected products

• Opensips Opensips: from 3.4.0, before 3.6.6 (fixed in 3.6.6); from 4.0.0-beta, before 4.0.0-rc1 (fixed in 4.0.0-rc1)

Published 2026-08-05. Last modified 2026-09-08.