What happened?

A buffer overflow has been discovered in the WebDAV service in Internet Information Services ISS 6.0 in Microsoft Windows Server 2003 R2. The vulnerability can lead to remote code execution (RCE) but it can only be exploited if the WebDAV service is enabled.

Details of the vulnerability

Buffer overflow in the ScStoragePathFromUrl function in the WebDAV service in Internet Information Services (IIS) 6.0 in Microsoft Windows Server 2003 R2 allows remote attackers to execute arbitrary code via a long header beginning with "If: <http://" in a PROPFIND request, as exploited in the wild in July or August 2016.

Web Distributed Authoring and Versioning (WebDAV) is an extension of the Hypertext Transfer Protocol (HTTP) that allows clients to perform remote Web content authoring operations. WebDAV is defined in RFC 4918 by a working group of the Internet Engineering Task Force.

The PROPFIND method retrieves properties, stored as XML, from a web resource. It is also overloaded to allow one to retrieve the collection structure (also known as directory hierarchy) of a remote system.

Sources:

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-7269

https://en.wikipedia.org/wiki/WebDAV

DenyAll Statement

Rules can be added on DenyAll WAF to block this specific vulnerability.

DenyAll WAF and i-Suite products:

In your ICX configuration, conditions on the request method and the 'If' header will be enough to simply mitigate the vulnerability:

ICX Engine mitigation is available in the following backup: ICX Configuration - CVE-2017-7269 Mitigation.backup

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