CVE-2026-45809: OpenSIPS: Denial of Service in watcherinfo XML generation from oversized watcher URI
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 handlesubscribe() and allow watcherinfo (presence.winfo) generation. The issue is configuration-dependent because the presence and presencexml 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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
OpenSIPSto a version that resolves this vulnerability.Fixed in 3.6.6 - Upgrade
Upgrade
OpenSIPSto a version that resolves this vulnerability.Fixed in 4.0.0-rc1
Event History
Frequently Asked Questions
What is the severity of CVE-2026-45809?
CVE-2026-45809 has a risk rating of 40, indicating a significant concern for denial of service.
How do I fix CVE-2026-45809?
To fix CVE-2026-45809, upgrade to OpenSIPS version 3.6.6 or 4.0.0-rc1 or later.
What type of vulnerability is CVE-2026-45809?
CVE-2026-45809 is a denial of service vulnerability related to oversized watcher URI handling in OpenSIPS.
Which versions are affected by CVE-2026-45809?
CVE-2026-45809 affects OpenSIPS versions prior to 3.6.6 and 4.0.0-rc1.
What can an attacker do with CVE-2026-45809?
An attacker can exploit CVE-2026-45809 by sending a specially crafted SUBSCRIBE Event: presence request to trigger a denial of service.