CVE-2026-31221: Pytorch lightning PyTorch Lightning Load_from_checkpoint Has An Vulnerability

HIGH
Advisory Identifier: GHSA-75m9-98v2-hjpm
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CVSS 7.8
CWE-502
Published
Advisory Summary

CVE-2026-31221 is a HIGH (CVSS 7.8) pytorch lightning load_from_checkpoint has an vulnerability (CWE-502: Deserialization of Untrusted Data) affecting Pytorch lightning libraries in the PyPI ecosystem. The issue involves pytorch lightning load_from_checkpoint has an insecure checkpoint deserialization. Remediation is available in the latest vendor maintenance releases.

CVE-2026-31221 at a Glance

CVE Identifier CVE-2026-31221
GHSA Identifier GHSA-75m9-98v2-hjpm
Severity HIGH
CVSS v3.1 Base Score 7.8
CWE Classification CWE-502: Deserialization of Untrusted Data
Affected Product Pytorch lightning
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H).

Attack Vector Local (AV:L)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2026-31221

To remediate this vulnerability, upgrade all affected Pytorch lightning dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

pytorch-lightning fixed: Latest secure release 
pip install pytorch-lightning>=Latest secure release
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show pytorch-lightning

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-31221, inspect your installed packages using pip:

pip show pytorch-lightning

Analyze the terminal output to locate any version of Pytorch lightning in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The pip show pytorch-lightning command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-502: Deserialization of Untrusted Data, where the product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid. In Pytorch lightning, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

PyTorch-Lightning versions 2.6.0 and earlier contain an insecure deserialization vulnerability (CWE-502) in the checkpoint loading mechanism. The LightningModule.load_from_checkpoint() method, which is commonly used to load saved model states, internally calls torch.load() without setting the security-restrictive weights_only=True parameter. This default behavior allows the deserialization of arbitrary Python objects via the Pickle module. A remote attacker can exploit this by providing a maliciously crafted checkpoint file, leading to arbitrary code execution on the victim's system when the file is loaded.

CVE-2026-31221 Affected Pytorch lightning Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
pytorch-lightning
pypi/pytorch-lightning
PyPI
≤ 2.6.0

References

NVD — CVE-2026-31221 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-31221
Pytorch lightning Source Repository REPOSITORY
https://github.com/Lightning-AI/pytorch-lightning
www.notion.so/cve-2026-31221-35d1... WEB
https://www.notion.so/CVE-2026-31221-35d1e1393188815f8db7c4fd08076639

Frequently Asked Questions

What is CVE-2026-31221?
CVE-2026-31221 is a security vulnerability in Pytorch lightning involving PyTorch Lightning load_from_checkpoint has an insecure checkpoint deserialization under CWE-502: Deserialization of Untrusted Data.
Which Pytorch lightning versions are affected?
Affected versions include releases prior to current release patches across affected packages: pytorch-lightning.
What version fixes CVE-2026-31221?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is pytorch-lightning affected?
Yes, pytorch-lightning is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of CVE-2026-31221?
CVE-2026-31221 has a CVSS v3.1 base score of 7.8 (HIGH) with vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-31221?
CVE-2026-31221 is classified under CWE-502: Deserialization of Untrusted Data (The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.).
How can I check PyPI dependencies for CVE-2026-31221?
Run the dependency tree command: 'pip show pytorch-lightning'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-75m9-98v2-hjpm",
  "modified" : "2026-05-18T20:24:38Z",
  "published" : "2026-05-12T18:30:38Z",
  "aliases" : [ "CVE-2026-31221" ],
  "summary" : "PyTorch Lightning load_from_checkpoint has an insecure checkpoint deserialization",
  "details" : "PyTorch-Lightning versions 2.6.0 and earlier contain an insecure deserialization vulnerability (CWE-502) in the checkpoint loading mechanism. The LightningModule.load_from_checkpoint() method, which is commonly used to load saved model states, internally calls torch.load() without setting the security-restrictive weights_only=True parameter. This default behavior allows the deserialization of arbitrary Python objects via the Pickle module. A remote attacker can exploit this by providing a maliciously crafted checkpoint file, leading to arbitrary code execution on the victim's system when the file is loaded.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "pytorch-lightning"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "2.6.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-31221"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/Lightning-AI/pytorch-lightning"
  }, {
    "type" : "WEB",
    "url" : "https://www.notion.so/CVE-2026-31221-35d1e1393188815f8db7c4fd08076639"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-502" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-18T20:24:38Z",
    "nvd_published_at" : "2026-05-12T16:16:14Z"
  }
}