Mitigating PHP2Shell: Everything You Need to Know
Easily map the attack path and prioritize which CVEs are a threat to your organization
Miggo AIGenerate vendor-ready rules for the observed attack patterns, plus reasoning and safe deployment guidance
Miggo AIRoot Cause AnalysisThe vulnerability is a 'fail-open' condition in NLTK's SSRF protection mechanism located in nltk/pathsec.py. The root cause lies in the interaction between two functions: _resolve_hostname and validate_network_url. The _resolve_hostname function is designed to resolve a hostname to IP addresses but has an exception handler that catches DNS errors (like OSError) and returns an empty list [] instead of raising an exception. The primary vulnerable function, validate_network_url, calls _resolve_hostname and iterates through the returned IP addresses to check against a blocklist. However, it does not check if the returned list is empty. If a DNS error occurs and an empty list is returned, the validation loop is skipped, and the function returns as if the URL was valid. This allows the urlopen function, which relies on this validation, to proceed with the request to the user-supplied URL without any IP-level security checks having been performed. This bypasses the intended SSRF protection, enabling an attacker to force requests to internal or restricted network endpoints, such as cloud provider metadata services, by triggering a DNS resolution failure.
| Package Name | Ecosystem | Vulnerable Versions | First Patched Version |
|---|---|---|---|
| nltk | pip | <= 3.9.4 | 3.10.0 |
