flash-attention contains an insecure deserialization vulnerability in its checkpoint loading mechanism

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

EPSS

• CVE-2026-31253: 0.22% estimated exploitation activity in the next 30 days; percentile 12.37 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

The flash-attention training framework thru commit e724e2588cbe754beb97cf7c011b5e7e34119e62 (2025-13-04) contains an insecure deserialization vulnerability (CWE-502) in its checkpoint loading mechanism. The loadcheckpoint() function in checkpoint.py and the checkpoint loading code in eval.py use torch.load() without enabling the security-restrictive weightsonly=True parameter. This allows the deserialization of arbitrary Python objects via the pickle module. An attacker can exploit this by providing a maliciously crafted checkpoint file. When a victim loads this checkpoint during model warmstarting or evaluation, arbitrary code is executed on the victim's system.

Published by the source

11 May 2026, 18:31 UTC

Last modified by the source

14 Jul 2026, 05:30 UTC

Source last checked

26 Oct 2026, 13:46 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-7g5w-pq96-8c5w

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-7g5w-pq96-8c5w

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# Patch Next advisory brief: CVE-2026-31253

Advisory: flash-attention contains an insecure deserialization vulnerability in its checkpoint loading mechanism
IDs: CVE-2026-31253, GHSA-7g5w-pq96-8c5w
Record: https://patchnext.com/advisories/cve-2026-31253 (revision 2, source checked 26 Oct 2026, 13:46 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI flash-attn: affected <= 2.8.3

## Suggested inspection (read-only)
- `python -m pip show flash-attn`: prints the installed version. Run with the environment that serves production active.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on flash-attn.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-7g5w-pq96-8c5w (OSV record GHSA-7g5w-pq96-8c5w lists affected ranges: PyPI flash-attn >=0 <=2.8.3)
- Verified: https://github.com/advisories/GHSA-7g5w-pq96-8c5w (GitHub-reviewed advisory GHSA-7g5w-pq96-8c5w lists affected ranges: PyPI flash-attn >=0 <=2.8.3)

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