Scapy Session Loading Vulnerable to Arbitrary Code Execution via Untrusted Pickle Deserialization
Summary
An unsafe deserialization vulnerability in Scapy <v2.7.0 allows attackers to execute arbitrary code when a malicious session file is locally loaded via the -s option. This requires convincing a user to manually load a malicious session file.
Details
Scapy’s interactive shell supports session loading using gzip-compressed pickle files:
```bash
./run_scapy -s <session_file.pkl.gz>
```
Internally, this triggers:
```python
# main.py
SESSION = pickle.load(gzip.open(session_name, "rb"))
```
Since no validation or restriction is performed on the deserialized object, any code embedded via __reduce__() will be executed immediately. This makes it trivial for an attacker to drop a malicious .pkl.gz in a shared folder and have it executed by unsuspecting users.
The vulnerability exists in the load_session function, which deserializes data using pickle.load() on .pkl.gz files provided via the -s CLI flag or programmatically through conf.session.
Affected lines in source code:
https://github.com/secdev/scapy/blob/master/scapy/main.py#L569-L572
```python
try:
s = pickle.load(gzip.open(fname, "rb"))
except IOError:
try:
s = pickle.load(open(fname, "rb"))
```
Impact
This is a classic deserialization vulnerability which leads to Code Execution (CE) when untrusted data is deserialized.
Any user who can trick another user into loading a crafted .pkl.gz session file (e.g. via -s option) can execute arbitrary Python code.
- Vulnerability type: Insecure deserialization (Python
pickle) - CWE: [CWE-502: Deserialization of Untrusted Data](https://cwe.mitre.org/data/definitions/502.html)
- CVSS v4.0 Vector:
CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N - CVSS Score: 5.4 (Medium)
- Impact: Arbitrary Code Execution
- Attack vector: Local or supply chain (malicious
.pkl.gz) - Affected users: Any user who loads session files (even interactively)
- Affected version: Scapy v2.6.1
Mitigations
- Do not use 'sessions' (the -s option when launching Scapy).
- Use the Scapy 2.7.0+ where the session mechanism has been removed.
