Inefficient Regular Expression Complexity
The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles.
Some regular expression engines have a feature called "backtracking". If the token cannot match, the engine "backtracks" to a position that may result in a different token that can match. Backtracking becomes a weakness if all of these conditions are met: - The number of possible backtracking attempts are exponential relative to the length of the input. - The input can fail to match the regular expression. - The input can be long enough. Attackers can create crafted inputs that intentionally cause the regular expression to use excessive backtracking in a way that causes the CPU consumption to spike.
Impact: DoS: Resource Consumption (CPU)
Effectiveness: High
Effectiveness: Moderate
Effectiveness: High
Effectiveness: Moderate
ID : DX-158
This example attempts to check if an input string is a "sentence" [REF-1164].Code Example:
var test_string = "Bad characters: $@#"; var bad_pattern = /^(\w+\s?)*$/i; var result = test_string.search(bad_pattern);
Code Example:
var test_string = "Bad characters: $@#"; var good_pattern = /^((?=(\w+))\2\s?)*$/i; var result = test_string.search(good_pattern);
Code Example:
my $test_string = "Bad characters: $@#"; my $bdrslt = $test_string; $bdrslt =~ /^(\w+\s?)*$/i;
Code Example:
my $test_string = "Bad characters: $@#"; my $gdrslt = $test_string; $gdrslt =~ /^((?=(\w+))\2\s?)*$/i;
High