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There are several national variants of ASCII. As a result, the original ASCII is often called US-ASCII. ISO/IEC 646-1991 defines a character set, similar to US-ASCII, but with code positions corresponding to US-ASCII characters @[]{|} as national use positions [ISO/IEC 646-1991]. It also gives some liberties with the characters #$^`~. In particular characters (e.g., #$^`~).  In ISO/IEC 646-1991, several national variants of ASCII are defined, assigning different letters and symbols to the national use positions. Consequently, the characters that appear in those positions, including those in US-ASCII, are less portable in international data transfer. Because of the national variants, some characters are less portable than others: they might be transferred or interpreted incorrectly.

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An implementation is free to define its own mapping of the "nonsafe" characters. For example, when run on Red Hat Enterprise Linux 7.5, this noncompliant code example resulted in the following file name being revealed by the ls command.:

?ngstr?m

Compliant Solution (File Name 1)

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Automated Detection

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

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