CWE-792: Incomplete Filtering of One or More Instances of Special Elements
Description
The product receives data from an upstream component, but does not completely filter one or more instances of special elements before sending it to a downstream component.
Submission Date :
Dec. 4, 2009, midnight
Modification Date :
2023-06-29 00:00:00+00:00
Organization :
MITRE
Extended Description
Incomplete filtering of this nature involves either:
- only filtering a single instance of a special element when more exist, or
- not filtering all instances or all elements where multiple special elements exist.
Example - 1
The following code takes untrusted input and uses a regular expression to filter "../" from the input. It then appends this result to the /home/user/ directory and attempts to read the file in the final resulting path. Since the regular expression does not have the /g global match modifier, it only removes the first instance of "../" it comes across. So an input value such as: will have the first "../" stripped, resulting in: This value is then concatenated with the /home/user/ directory: which causes the /etc/passwd file to be retrieved once the operating system has resolved the ../ sequences in the pathname. This leads to relative path traversal (CWE-23).
my $Username = GetUntrustedInput();$Username =~ s/\.\.\///;my $filename = "/home/user/" . $Username;ReadAndSendFile($filename);../../../etc/passwd../../etc/passwd/home/user/../../etc/passwd
Related Weaknesses
This table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined to give an overview of the different insight to similar items that may exist at higher and lower levels of abstraction.
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