The product uses a regular expression to perform neutralization, but the regular expression is not anchored and may allow malicious or malformed data to slip through.
When performing tasks such as validating against a set of allowed inputs (allowlist), data is examined and possibly modified to ensure that it is well-formed and adheres to a list of safe values. If the regular expression is not anchored, malicious or malformed data may be included before or after any string matching the regular expression. The type of malicious data that is allowed will depend on the context of the application and which anchors are omitted from the regular expression.
Threat Mapped score: 0.0
Industry: Finiancial
Threat priority: Unclassified
CVE: CVE-2022-30034
Chain: Web UI for a Python RPC framework does not use regex anchors to validate user login emails (CWE-777), potentially allowing bypass of OAuth (CWE-1390).
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| Phase | Note |
|---|---|
| Implementation | N/A |
Intro: Consider a web application that supports multiple languages. It selects messages for an appropriate language by using the lang parameter.
Body: The previous code attempts to match only alphanumeric values so that language values such as "english" and "french" are valid while also protecting against path traversal, CWE-22. However, the regular expression anchors are omitted, so any text containing at least one alphanumeric character will now pass the validation step. For example, the attack string below will match the regular expression.
$dir = "/home/cwe/languages"; $lang = $_GET['lang']; if (preg_match("/[A-Za-z0-9]+/", $lang)) { include("$dir/$lang"); } else { echo "You shall not pass!\n"; }Intro: This code uses a regular expression to validate an IP string prior to using it in a call to the "ping" command.
Body: 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.
import subprocess import re def validate_ip_regex(ip: str): ip_validator = re.compile(r"((25[0-5]|(2[0-4]|1\d|[1-9]|)\d)\.?\b){4}") if ip_validator.match(ip): return ip else: raise ValueError("IP address does not match valid pattern.") def run_ping_regex(ip: str): validated = validate_ip_regex(ip) # The ping command treats zero-prepended IP addresses as octal result = subprocess.call(["ping", validated]) print(result)