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CWE-1007

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CWE-1007

Insufficient Visual Distinction of Homoglyphs Presented to User

Base
Incomplete

Description

The product displays information or identifiers to a user, but the display mechanism does not make it easy for the user to distinguish between visually similar or identical glyphs (homoglyphs), which may cause the user to misinterpret a glyph and perform an unintended, insecure action.

{"xhtml:p":["Some glyphs, pictures, or icons can be semantically distinct to a program, while appearing very similar or identical to a human user. These are referred to as homoglyphs. For example, the lowercase \"l\" (ell) and uppercase \"I\" (eye) have different character codes, but these characters can be displayed in exactly the same way to a user, depending on the font. This can also occur between different character sets. For example, the Latin capital letter \"A\" and the Greek capital letter \"Α\" (Alpha) are treated as distinct by programs, but may be displayed in exactly the same way to a user. Accent marks may also cause letters to appear very similar, such as the Latin capital letter grave mark \"À\" and its equivalent \"Á\" with the acute accent.","Adversaries can exploit this visual similarity for attacks such as phishing, e.g. by providing a link to an attacker-controlled hostname that looks like a hostname that the victim trusts. In a different use of homoglyphs, an adversary may create a back door username that is visually similar to the username of a regular user, which then makes it more difficult for a system administrator to detect the malicious username while reviewing logs."]}

Common Consequences

Scope

Integrity
Confidentiality

Impact

Other

Potential Mitigations

Implementation

Use a browser that displays Punycode for IDNs in the URL and status bars, or which color code various scripts in URLs. Due to the prominence of homoglyph attacks, several browsers now help safeguard against this attack via the use of Punycode. For example, Mozilla Firefox and Google Chrome will display IDNs as Punycode if top-level domains do not restrict which characters can be used in domain names or if labels mix scripts for different languages.

Implementation

Use an email client that has strict filters and prevents messages that mix character sets to end up in a user's inbox. Certain email clients such as Google's GMail prevent the use of non-Latin characters in email addresses or in links contained within emails. This helps prevent homoglyph attacks by flagging these emails and redirecting them to a user's spam folder.

CVE-2013-7236

web forum allows impersonation of users with homoglyphs in account names

CVE-2012-0584

Improper character restriction in URLs in web browser

CVE-2009-0652

Incomplete denylist does not include homoglyphs of "/" and "?" characters in URLs

CVE-2017-5015

web browser does not convert hyphens to punycode, allowing IDN spoofing in URLs

CVE-2005-0233

homoglyph spoofing using punycode in URLs and certificates

CVE-2005-0234

homoglyph spoofing using punycode in URLs and certificates

CVE-2005-0235

homoglyph spoofing using punycode in URLs and certificates

Applicable Platforms

Not Language-Specific

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