Title: Microsoft IIS ISAPI Filter Access Violation Denial of Service Vulnerability
Severity: MODERATE
Description:
A vulnerability has been identified in the way Microsoft Internet Information Server handles URL errors. This vulnerability exists on IIS servers that also have Front Page Server Extensions or ASP.NET installed.
If a certain ISAPI filter that is installed with Front Page Server Extensions and ASP.NET receives a URL that exceeds the maximum allowable length, the IIS service will fail. This is because the ISAPI filter fails the request and sets the URL to a null value. When IIS receives the null value, it still tries to process the request before sending the error message back to the requester. This results in an access violation error which causes the IIS service to fail.
On IIS 4.0 servers, the IIS service would have to be manually restarted to resume normal operation. On IIS 5.0 and 5.1 servers, the service will automatically restart itself.
So far, Microsoft has only identified this issue in one ISAPI filter that is installed with Front Page Server Extensions and ASP.NET, however, there is a possibility that other ISAPI filters could contain the same behaviour. The vulnerability is not within the ISAPI filter itself, but with the way that IIS handles the null value returned by the filter.
Custom ISAPI filters may also be affected by this condition.
It is important to note that this BugTraq ID is an individual vulnerability entry to followup the aggregated Multiple Remote IIS Vulnerabilities alert released by SecurityFocus.
A number of Cisco products are affected by this vulnerability, although this issue is not present in the Cisco products themselves.
Affected Products:
- Cisco Building Broadband Service Manager 4.0.1
- Cisco Building Broadband Service Manager 4.2.0
- Cisco Building Broadband Service Manager 4.3.0
- Cisco Building Broadband Service Manager 4.4.0
- Cisco Building Broadband Service Manager 4.5.0
- Cisco Building Broadband Service Manager 5.0.0
- Cisco Building Broadband Service Manager 5.1.0
- Cisco Call Manager 1.0.0
- Cisco Call Manager 2.0.0
- Cisco Call Manager 3.0.0
- Cisco Call Manager 3.1.0
- Cisco Call Manager 3.2.0
- Cisco ICS 7750 0.0.0
- Cisco IP/VC 3540 Video Rate Matching Module 0.0.0
- Cisco Unity Server 2.0.0
- Cisco Unity Server 2.1.0
- Cisco Unity Server 2.2.0
- Cisco Unity Server 2.3.0
- Cisco Unity Server 2.4.0
- Cisco VoIP Phone 7902G
- Cisco VoIP Phone 7905G
- Cisco VoIP Phone 7912G
- Cisco uOne 1.0.0
- Cisco uOne 2.0.0
- Cisco uOne 3.0.0
- Cisco uOne 4.0.0
- Microsoft BackOffice 4.0.0
- Microsoft BackOffice 4.5.0
- Microsoft IIS 4.0.0
- Microsoft IIS 5.0
- Microsoft IIS 5.1.0
- Microsoft Windows 2000 Advanced Server
- Microsoft Windows 2000 Professional
- Microsoft Windows 2000 Server
- Microsoft Windows NT 4.0 Option Pack
- Microsoft Windows XP 64-bit Edition
- Microsoft Windows XP 64-bit Edition SP1
- Microsoft Windows XP Professional
- Microsoft Windows XP Professional SP1
References:
- CERT/CC: Vulnerability Note VU#521059
- Microsoft: Microsoft Security Bulletin MS02-018
- Microsoft: Q317636 Windows NT Server 4.0, Terminal Server Edition, Security Rollup Package
- Microsoft: Technet Security
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