CVE-2026-45809
OpenSIPS remote DoS via oversized SUBSCRIBE watcher URI causing worker crash
Is CVE-2026-45809 being exploited?
Not confirmed. CVE-2026-45809 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.39% probability of exploitation in the next 30 days.
How severe is CVE-2026-45809?
CVE-2026-45809 is rated High with a CVSS score of 8.7. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-45809?
Yes. A fix has been recorded for CVE-2026-45809. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-45809 affect?
CVE-2026-45809 affects OpenSIPS versions prior to 3.6.6, OpenSIPS versions prior to 4.0.0-rc1, deployments loading presence and presence_xml modules, systems exposing handle_subscribe(). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-45809?
Upgrade to OpenSIPS 3.6.6 or later and restrict/validate SUBSCRIBE access
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote attacker can send a crafted SUBSCRIBE with a long From URI to trigger a stack overflow and crash an OpenSIPS worker, causing denial of service.
Immediate action required
- affected>= 3.4.0 and < 3.6.6
- affected>= 4.0.0-beta and < 4.0.0-rc1
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.