Improper Neutralization of Invalid Characters in Identifiers in Web Pages
|ID: 86||Date: (C)2012-05-14 (M)2012-11-08|
|Type: weakness||Status: DRAFT|
|Abstraction Type: Variant|
The software does not neutralize or incorrectly neutralizes
invalid characters or byte sequences in the middle of tag names, URI schemes,
and other identifiers.
Extended DescriptionSome web browsers may remove these sequences, resulting in output that
may have unintended control implications. For example, the software may
browsers, allowing XSS or other attacks.
Applicable PlatformsLanguage Class: All
Time Of Introduction
Related Attack Patterns
|ConfidentialityIntegrityAvailability ||Read application
dataExecute unauthorized code or
commands || |
|Implementation ||Output Encoding ||Use and specify an output encoding that can be handled by the
downstream component that is reading the output. Common encodings
include ISO-8859-1, UTF-7, and UTF-8. When an encoding is not specified,
a downstream component may choose a different encoding, either by
assuming a default encoding or automatically inferring which encoding is
being used, which can be erroneous. When the encodings are inconsistent,
the downstream component might treat some character or byte sequences as
special, even if they are not special in the original encoding.
Attackers might then be able to exploit this discrepancy and conduct
injection attacks; they even might be able to bypass protection
mechanisms that assume the original encoding is also being used by the
downstream component.The problem of inconsistent output encodings often arises in web
pages. If an encoding is not specified in an HTTP header, web browsers
often guess about which encoding is being used. This can open up the
browser to subtle XSS attacks. || || |
|Implementation ||Identify and Reduce Attack Surface ||To help mitigate XSS attacks against the user's session cookie, set
the session cookie to be HttpOnly. In browsers that support the HttpOnly
feature (such as more recent versions of Internet Explorer and Firefox),
this attribute can prevent the user's session cookie from being
accessible to malicious client-side scripts that use document.cookie.
This is not a complete solution, since HttpOnly is not supported by all
browsers. More importantly, XMLHTTPRequest and other powerful browser
technologies provide read access to HTTP headers, including the
Set-Cookie header in which the HttpOnly flag is set. ||Defense in Depth || |
|CWE-86 ChildOf CWE-896 ||Category ||CWE-888 || |
- CVE-2004-0595 : XSS filter doesn't filter null characters before looking for dangerous tags, which are ignored by web browsers. Multiple Interpretation Error (MIE) and validate-before-cleanse.
For more examples, refer to CVE relations in the bottom box.
White Box Definitions None
Black Box Definitions None
|PLOVER || ||Invalid Characters in Identifiers || |