How severe is CVE-2006-1651?

CVE-2006-1651 has a CVSS 2.0 base score of 7.5, rated high severity.

Is CVE-2006-1651 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 15% (96th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2006-1651?

CVE-2006-1651 affects Microsoft Isa Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2006-1651?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2006-1651 published?

CVE-2006-1651 was published on 2006-04-06 and last updated on 2026-06-16.

CVE-2006-1651

CVE-2006-1651 is a high-severity vulnerability in Microsoft Isa Server with a CVSS 2.0 base score of 7.5. Its EPSS exploit-prediction score of 15% places it in the 96th percentile, indicating an elevated likelihood of exploitation.

Key facts

Severity: High (CVSS 2.0 base score 7.5)
EPSS exploit prediction: 15% (96th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Microsoft Isa Server
Published: 2006-04-06
Last modified: 2026-06-16

Description

Microsoft ISA Server 2004 allows remote attackers to bypass certain filtering rules, including ones for (1) ICMP and (2) TCP, via IPv6 packets. NOTE: An established researcher has disputed this issue, saying that "Neither ISA Server 2004 nor Windows 2003 Basic Firewall support IPv6 filtering ... This is different network protocol.

Frequently asked questions

What is CVE-2006-1651?: Microsoft ISA Server 2004 allows remote attackers to bypass certain filtering rules, including ones for (1) ICMP and (2) TCP, via IPv6 packets. NOTE: An established researcher has disputed this issue, saying that "Neither ISA Server 2004 nor Windows 2003 Basic Firewall support IPv6 filtering ... This is different network protocol.
How severe is CVE-2006-1651?: CVE-2006-1651 has a CVSS 2.0 base score of 7.5, rated high severity.
Is CVE-2006-1651 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 15% (96th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2006-1651?: CVE-2006-1651 affects Microsoft Isa Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2006-1651?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2006-1651 published?: CVE-2006-1651 was published on 2006-04-06 and last updated on 2026-06-16.

References

Affected products (1)

cpe:2.3:a:microsoft:isa_server:2004:*:*:*:*:*:*:*

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