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Microsoft IIS Escape Character Parsing Vulnerability

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Microsoft IIS Escape Character Parsing Vulnerability

Severity
6
CVSS
(AV:N/AC:L/Au:N/C:P/I:P/A:N)
Published
12/21/1999
Created
07/25/2018
Added
11/01/2004
Modified
07/31/2012

Description

IIS accepts escaped characters that are not valid hexadecimal digits. All webservers that are compliant with RFC 1738 accept hexadecimal digits that are preceded by a percent sign, but IIS will also accept invalid hex digits and translate some of them into valid ASCII characters. This provides a third means of constructing URLs (plaintext, valid hex, and invalid hex) that may be used to bypass third-party access control mechanisms and intrusion detection systems. This issue does not provide a means of compromising the IIS server itself.

Solution(s)

  • http-iis-0031

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