Horovod contains an insecure deserialization vulnerability in its KVStore HTTP server component

Exploitation

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

CVSS

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

EPSS

• CVE-2026-31234: 0.69% estimated exploitation activity in the next 30 days; percentile 52.73 (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.

Horovod thru 0.28.1 contains an insecure deserialization vulnerability (CWE-502) in its KVStore HTTP server component. The KVStore server, used for distributed task coordination, lacks authentication and authorization controls, allowing any remote attacker to write arbitrary data via HTTP PUT requests. When a Horovod worker reads data from the KVStore (via HTTP GET), it deserializes the data using cloudpickle.loads() without verifying its source or integrity. An attacker can exploit this by sending a malicious pickle payload to the server before the legitimate data is written, causing the victim worker to deserialize and execute arbitrary code, leading to remote code execution.

Published by the source

12 May 2026, 18:30 UTC

Last modified by the source

27 Oct 2026, 16:45 UTC

Source last checked

28 Oct 2026, 06:10 UTC

1. Revision 5 · amended · 28 Oct 2026

   Amended from osv record GHSA-mf8f-x4r3-jm8c

2. Revision 4 · amended · 27 Oct 2026

   Amended from ghsa record GHSA-mf8f-x4r3-jm8c

3. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-mf8f-x4r3-jm8c

4. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-mf8f-x4r3-jm8c

5. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-mf8f-x4r3-jm8c

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# Patch Next advisory brief: CVE-2026-31234

Advisory: Horovod contains an insecure deserialization vulnerability in its KVStore HTTP server component
IDs: CVE-2026-31234, GHSA-mf8f-x4r3-jm8c
Record: https://patchnext.com/advisories/cve-2026-31234 (revision 5, source checked 28 Oct 2026, 06:10 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
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 horovod: affected <= 0.28.1

## Suggested inspection (read-only)
- `python -m pip show horovod`: 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 horovod.
- 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://github.com/advisories/GHSA-mf8f-x4r3-jm8c (GitHub-reviewed advisory GHSA-mf8f-x4r3-jm8c lists affected ranges: PyPI horovod >=0 <=0.28.1)
- Verified: https://osv.dev/vulnerability/GHSA-mf8f-x4r3-jm8c (OSV record GHSA-mf8f-x4r3-jm8c lists affected ranges: PyPI horovod >=0 <=0.28.1)

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