CVE-2026-45537
OpenSIPS buffer overflow in construct_uri() lets attackers alter SIP routing via long username.
Is CVE-2026-45537 being exploited?
Not confirmed. CVE-2026-45537 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 0.35% probability of exploitation in the next 30 days.
How severe is CVE-2026-45537?
CVE-2026-45537 is rated Critical with a CVSS score of 9.1. 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-2026-45537?
Yes. A fix has been recorded for CVE-2026-45537. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-45537 affect?
CVE-2026-45537 affects OpenSIPS < 3.6.6, OpenSIPS < 4.0.0-rc1, SIP infrastructures using OpenSIPS. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-45537?
Upgrade to OpenSIPS 3.6.6 or 4.0.0-rc1; validate/limit username length and monitor SIP logs.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote overflow via SIP username lets attacker overwrite globals, flip 503 translation flag and modify/redirect SIP routing and call handling.
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.