CWE-625: Permissive Regular Expression
Description
The product uses a regular expression that does not sufficiently restrict the set of allowed values.
Submission Date :
May 7, 2007, midnight
Modification Date :
2023-06-29 00:00:00+00:00
Organization :
MITRE
Extended Description
This effectively causes the regexp to accept substrings that match the pattern, which produces a partial comparison to the target. In some cases, this can lead to other weaknesses. Common errors include:
- not identifying the beginning and end of the target string
- using wildcards instead of acceptable character ranges
- others
Example - 1
The following code takes phone numbers as input, and uses a regular expression to reject invalid phone numbers. An attacker could provide an argument such as: "; ls -l ; echo 123-456" This would pass the check, since "123-456" is sufficient to match the "\d+-\d+" portion of the regular expression.
// # looks like it only has hyphens and digits//
system("lookup-phone $phone");
error("malformed number!");$phone = GetPhoneNumber();if ($phone =~ /\d+-\d+/) {}else {}
Example - 2
This code uses a regular expression to validate an IP string prior to using it in a call to the "ping" command. Since the regular expression does not have anchors (CWE-777), i.e. is unbounded without ^ or $ characters, then prepending a 0 or 0x to the beginning of the IP address will still result in a matched regex pattern. Since the ping command supports octal and hex prepended IP addresses, it will use the unexpectedly valid IP address (CWE-1389). For example, "0x63.63.63.63" would be considered equivalent to "99.63.63.63". As a result, the attacker could potentially ping systems that the attacker cannot reach directly.
return ip
raise ValueError("IP address does not match valid pattern.")ip_validator = re.compile(r"((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\.?\b){4}")if ip_validator.match(ip):else:
// # The ping command treats zero-prepended IP addresses as octal//
validated = validate_ip_regex(ip)result = subprocess.call(["ping", validated])print(result)import subprocessimport redef validate_ip_regex(ip: str):def run_ping_regex(ip: str):
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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