Zero-day vulnerability in Microsoft IIS

Improper input validation
CVE-2009-2521

The issue has been introduced in 02/17/2000. The weakness was disclosed on 09/04/2009 by Kingcope.

Vulnerability details

Advisory: SB2009083101 - Two vulnerabilities in Microsoft IIS FTP server

Vulnerable component: Microsoft IIS

CVE-ID: CVE-2009-2521

CVSSv3 score: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:F/RL:O/RC:C

CWE-ID: CWE-20 - Improper input validation

Description:

The vulnerability allows a remote authenticated attacker to cause DoS conditions on the target system.

The weakness exists due to an error when processing recursive directory listing commands by the FTP Service. By sending a specially crafted LIST command containing wildcard characters, a remote attacker can trigger the FTP service to crash.

Successful exploitation of the vulnerability results in denial of service on the vulnerable system.

Note: the vulnerability was being actively exploited.

Public Exploits:

- Microsoft IIS 7.0 FTP Server - Stack Exhaustion Denial of Service (MS09-053) (Metasploit) [Exploit-DB]

- Microsoft IIS 5.0/6.0 FTP Server - (Stack Exhaustion) Denial of Service [Exploit-DB]

External links:

https://technet.microsoft.com/en-us/library/security/ms09-053.aspx
https://vulners.com/metasploit/MSF:AUXILIARY/DOS/WINDOWS/FTP/IIS_LIST_EXHAUSTION
https://www.auscert.org.au/render.html?it=11563

About zero-day vulnerabilities

Zero-day vulnerability is an undisclosed vulnerability in software that hackers can exploit to compromise computer programs, gain unauthorized access to sensitive data, penetrate networks, etc. We consider vulnerability a zero-day when there is no solution provided from software vendor and the vulnerability is being actively exploited by malicious actors.

Zero-day candidate is a potential zero-day vulnerability in software which might have been used in targeted attacks, however there is no evidence to support this suggestion.