Nortel UNIStim protocol, as used in Communication Server 1000 and other products, uses predictable sequence numbers, which allows remote attackers to hijack sessions via sniffing or brute force attacks.
Conclusion & alert: CVE-2008-6564 is rated Moderate Risk (59.1/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.94%). Mandatory action: Review affected assets and schedule remediation.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2025-08-20 | 2.17% | 1.94% | -0.23% |
| 2 | 2025-03-30 | 2.95% | 2.17% | -0.78% |
| 3 | 2025-03-29 | — | 2.95% | — |
Full EPSS history (7 records total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 7.6 | 2.0 | HIGH |
|
4.9 | 10.0 | [email protected] |
| Vendor | Product | Version | Raw CPE |
|---|---|---|---|
| nortel | communication_server_1000 | — | cpe:2.3:a:nortel:communication_server_1000:*:*:*:*:*:*:*:* |
| nortel | unistim_protocol | — | cpe:2.3:h:nortel:unistim_protocol:*:*:*:*:*:*:*:* |