CVE-2026-45538
Stack overflow in OpenSIPS sip_to_json allows unauthenticated RCE via crafted SIP header.
Is CVE-2026-45538 being exploited?
Not confirmed. CVE-2026-45538 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 0.58% probability of exploitation in the next 30 days.
How severe is CVE-2026-45538?
CVE-2026-45538 is rated Critical with a CVSS score of 9.8. 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-2026-45538?
Yes. A fix has been recorded for CVE-2026-45538. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-45538 affect?
CVE-2026-45538 affects OpenSIPS <= 4.0.0 (when routing scripts call sip_to_json), SIP-based VoIP infrastructure using OpenSIPS. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-45538?
Block/inspect UDP 5060, apply IDS/IPS signatures, restrict OpenSIPS access, and patch when vendor release is available.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unauthenticated UDP packet with an oversized SIP header can crash the process or achieve remote code execution by overwriting return address.
Immediate action required
- affected<= 4.0.0
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.