How severe is CVE-2001-1533?

CVE-2001-1533 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2001-1533 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 18% (97th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2001-1533?

CVE-2001-1533 affects Microsoft Isa Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2001-1533?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2001-1533 published?

CVE-2001-1533 was published on 2001-12-31 and last updated on 2026-06-16.

CVE-2001-1533

CVE-2001-1533 is a medium-severity vulnerability in Microsoft Isa Server with a CVSS 3.x base score of 5.3. Its EPSS exploit-prediction score of 18% places it in the 97th percentile, indicating an elevated likelihood of exploitation.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
CVSS v2: 5.0
EPSS exploit prediction: 18% (97th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Microsoft Isa Server
Published: 2001-12-31
Last modified: 2026-06-16

Description

Microsoft Internet Security and Acceleration (ISA) Server 2000 allows remote attackers to cause a denial of service via a flood of fragmented UDP packets. NOTE: the vendor disputes this issue, saying that it requires high bandwidth to exploit, and the server does not experience any instability. Therefore this "laws of physics" issue might not be included in CVE

Frequently asked questions

What is CVE-2001-1533?: Microsoft Internet Security and Acceleration (ISA) Server 2000 allows remote attackers to cause a denial of service via a flood of fragmented UDP packets. NOTE: the vendor disputes this issue, saying that it requires high bandwidth to exploit, and the server does not experience any instability. Therefore this "laws of physics" issue might not be included in CVE
How severe is CVE-2001-1533?: CVE-2001-1533 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2001-1533 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 18% (97th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2001-1533?: CVE-2001-1533 affects Microsoft Isa Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2001-1533?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2001-1533 published?: CVE-2001-1533 was published on 2001-12-31 and last updated on 2026-06-16.

References

Affected products (1)

cpe:2.3:a:microsoft:isa_server:2000:*:*:*:*:*:*:*

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