The product receives data from an upstream component, but only accounts for special elements at a specified location, thereby missing remaining special elements that may exist before sending it to a downstream component.
A filter might only account for instances of special elements when they occur: relative to a marker (e.g. "at the beginning/end of string; the second argument"), or at an absolute position (e.g. "byte number 10"). This may leave special elements in the data that did not match the filter position, but still may be dangerous.
Threat Mapped score: 0.0
Industry: Finiancial
Threat priority: Unclassified
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| Phase | Note |
|---|---|
| Implementation | REALIZATION: This weakness is caused during implementation of an architectural security tactic. |
Intro: The following code takes untrusted input and uses a regular expression to filter a "../" element located at the beginning of the input string. It then appends this result to the /home/user/ directory and attempts to read the file in the final resulting path.
Body: Since the regular expression is only looking for an instance of "../" at the beginning of the string, it only removes the first "../" element. So an input value such as:
my $Username = GetUntrustedInput(); $Username =~ s/^\.\.\///; my $filename = "/home/user/" . $Username; ReadAndSendFile($filename);Intro: The following code takes untrusted input and uses a substring function to filter a 3-character "../" element located at the 0-index position of the input string. It then appends this result to the /home/user/ directory and attempts to read the file in the final resulting path.
Body: Since the if function is only looking for a substring of "../" between the 0 and 2 position, it only removes that specific "../" element. So an input value such as:
my $Username = GetUntrustedInput(); if (substr($Username, 0, 3) eq '../') { $Username = substr($Username, 3); } my $filename = "/home/user/" . $Username; ReadAndSendFile($filename);