CVE-2008-6564: Nortel UNIStim protocol, as used in Communication Server 1000 and other products, uses predictable sequence nu

This month

HIGH 7.6MITIGATEMITIGATE

CVE-2008-6564 is a high-severity flaw (CVSS 7.6) affecting communication server 1000, unistim protocol. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

High severity

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.6 (High)
EPSS exploit chance	2.2% (top 17%)
CISA exploited list	No
Published	2009-03-31
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: nortel

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2009-03-31 17:30 UTCPublished CVE record published
2026-06-16 23:02 UTCUpdated Record last modified

nortel communication server 1000 MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy communication-server-1000 || rpm -q communication-server-1000 || communication-server-1000 --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

nortel unistim protocol MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

Firmware

Install the latest firmware from the vendor advisory; if none, apply the vendor workaround.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2008-6564?

communication server 1000: mitigate or apply the listed mitigation; unistim protocol: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2008-6564 being exploited?

CVE-2008-6564 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2008-6564 affect?

CVE-2008-6564 affects communication server 1000, unistim protocol. Severity is high (CVSS 7.6). 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.

How urgent is CVE-2008-6564?

Priority 47/100. High severity

References

← Back to latest CVEs