How severe is CVE-2026-31221?

CVE-2026-31221 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-31221 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (31st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-31221?

CVE-2026-31221 affects Lightningai Pytorch Lightning. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-31221?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-31221 have an EU (EUVD) identifier?

Yes. CVE-2026-31221 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-29505.

When was CVE-2026-31221 published?

CVE-2026-31221 was published on 2026-05-12 and last updated on 2026-06-17.

CVE-2026-31221

CVE-2026-31221 is a high-severity vulnerability in Lightningai Pytorch Lightning with a CVSS 3.x base score of 7.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-502.

Key facts

Severity: High (CVSS 3.x base score 7.8)
EPSS exploit prediction: 0% (31st percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-29505
Weakness: CWE-502
Affected product: Lightningai Pytorch Lightning
Published: 2026-05-12
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2026-31221?: 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.
How severe is CVE-2026-31221?: CVE-2026-31221 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-31221 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (31st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-31221?: CVE-2026-31221 affects Lightningai Pytorch Lightning. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-31221?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-31221 have an EU (EUVD) identifier?: Yes. CVE-2026-31221 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-29505.
When was CVE-2026-31221 published?: CVE-2026-31221 was published on 2026-05-12 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:lightningai:pytorch_lightning:*:*:*:*:*:python:*:*

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