How severe is CVE-2009-2521?

CVE-2009-2521 has a CVSS 2.0 base score of 5.0, rated medium severity.

Is CVE-2009-2521 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 82% (100th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2009-2521?

CVE-2009-2521 affects Microsoft Internet Information Services. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2009-2521?

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

When was CVE-2009-2521 published?

CVE-2009-2521 was published on 2009-09-04 and last updated on 2026-06-16.

CVE-2009-2521

CVE-2009-2521 is a medium-severity vulnerability in Microsoft Internet Information Services with a CVSS 2.0 base score of 5.0. Its EPSS exploit-prediction score of 82% places it in the 100th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-400.

Key facts

Severity: Medium (CVSS 2.0 base score 5.0)
EPSS exploit prediction: 82% (100th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-400
Affected product: Microsoft Internet Information Services
Published: 2009-09-04
Last modified: 2026-06-16

Description

Stack consumption vulnerability in the FTP Service in Microsoft Internet Information Services (IIS) 5.0 through 7.0 allows remote authenticated users to cause a denial of service (daemon crash) via a list (ls) -R command containing a wildcard that references a subdirectory, followed by a .. (dot dot), aka "IIS FTP Service DoS Vulnerability."

Frequently asked questions

What is CVE-2009-2521?: Stack consumption vulnerability in the FTP Service in Microsoft Internet Information Services (IIS) 5.0 through 7.0 allows remote authenticated users to cause a denial of service (daemon crash) via a list (ls) -R command containing a wildcard that references a subdirectory, followed by a .. (dot dot), aka "IIS FTP Service DoS Vulnerability."
How severe is CVE-2009-2521?: CVE-2009-2521 has a CVSS 2.0 base score of 5.0, rated medium severity.
Is CVE-2009-2521 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 82% (100th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2009-2521?: CVE-2009-2521 affects Microsoft Internet Information Services. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2009-2521?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2009-2521 published?: CVE-2009-2521 was published on 2009-09-04 and last updated on 2026-06-16.

References

Affected products (1)

cpe:2.3:a:microsoft:internet_information_services:*:*:*:*:*:*:*:*

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Browse all CWE-400 (Uncontrolled Resource Consumption) vulnerabilities →

Threat intelligence

Threat-intel indicators referencing this CVE:

200.71.154.142 (ipv4-addr)
131.161.184.46 (ipv4-addr)
200.57.190.209 (ipv4-addr)
190.111.226.20 (ipv4-addr)