How severe is CVE-2025-71373?

No CVSS score has been assigned to CVE-2025-71373 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2025-71373?

CVE-2025-71373 affects the following packages: picklescan (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2025-71373?

Update picklescan to 0.0.33 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-71373 is resolved across your whole dependency graph.

How do I detect CVE-2025-71373 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for picklescan, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2025-71373 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2025-71373 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-71373 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-71373?

CVE-2025-71373 has an EPSS (Exploit Prediction Scoring System) score of 0.6%, placing it in the 48th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-71373?

CVE-2025-71373 is classified as CWE-693 (CWE-693). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2025-71373 published, and has it been updated?

CVE-2025-71373 was published on July 4, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2025-71373 — picklescan

Fix: mmaitre314/picklescan#53

CVE-2025-71373 is a CWE-693 vulnerability in picklescan. A fix is available for picklescan — see the affected versions and patch details below.

picklescan - Remote Code Execution via operator.methodcaller Detection Bypass

Also known asGHSA-x843-g5mx-g377

Published

Jul 4, 2026

Updated

Aug 12, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 29, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-71373.

EPSS Exploitation Probability

via FIRST.org ↗

0.6%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs48th percentile — riskier than 48% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍picklescan

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Summary

Picklescan uses operator.methodcaller, which is a built-in python library function to execute remote pickle files.

Details

The attack payload executes in the following steps:

First, the attacker crafts the payload by calling the operator.methodcaller function in method reduce.
Then, when the victim checks whether the pickle file is safe using the Picklescan library and this library doesn't detect any dangerous functions, they decide to use pickle.load() on this malicious pickle file, thus leading to remote code execution.

PoC

import pickle
import pickletools
opcode1 = b'''cbuiltins
__import__
(Vos
tRp0
0coperator
methodcaller
(Vsystem
Vecho "pwned by operator.methodcaller"
tR(g0
tR.'''
pickletools.dis(opcode1)
pickle.loads(opcode1)

This PoC can't be easily created by pickle.dumps, therefore it was manually built.

Impact

Any organization or individual relying on picklescan to detect malicious pickle files inside PyTorch models. Attackers can embed malicious code in pickle file that remains undetected but executes when the pickle file is loaded. Attackers can distribute infected pickle files across ML models, APIs, or saved Python objects.

Report by

Pinji Chen ([email protected]) from the NISL lab (https://netsec.ccert.edu.cn/about) at Tsinghua University, Guanheng Liu ([email protected]).

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`picklescan`	all versions	0.0.33`pip install --upgrade 'picklescan==0.0.33'`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for picklescan, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update picklescan to 0.0.33 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-71373 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### Summary Picklescan uses `operator.methodcaller`, which is a built-in python library function to execute remote pickle files. ### Details The attack payload executes in the following steps: - First, the attacker crafts the payload by calling the `operator.methodcaller` function in method `reduce`. - Then, when the victim checks whether the pickle file is safe using the Picklescan library and this library doesn't detect any dangerous functions, they decide to use pickle.load() on this malicious pickle file, thus leading to remote code execution. ### PoC ``` import pickle import pickletool

O3 Security · Impact-Aware SCA

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