CVE-2009-2521

What it is

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."

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

82.3% chance of exploitation in the next 30 days (EPSS). Higher than most.

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2009-09-04 10:30 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-16 23:09 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 82.3% in the next 30 days (EPSS).
• Severity: 5.0 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2009-09-04 10:30 UTC

Last modified

2026-06-16 23:09 UTC

Exploit probability

82.3% · EPSS, next 30 days

Weakness

CWE-400 · Uncontrolled resource consumption

Record status

Modified

Affected

• Microsoft Internet Information Services ≤ 7.0

Attack profile CVSS 2.0 · 5.0

Attack vector

Network

Complexity

Low

Authentication

None

Confidentiality

None

Integrity

None

Availability

Partial

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2009-2521.md and follow it. Check whether this project is affected by CVE-2009-2521. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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