---
id: CVE-2026-31234
aliases:
  - GHSA-mf8f-x4r3-jm8c
  - PYSEC-2026-354
title: >-
  Horovod contains an insecure deserialization vulnerability in its KVStore HTTP
  server component
summary: >-
  Horovod contains an insecure deserialization vulnerability in its KVStore HTTP
  server component
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
vendor: horovod
product: horovod
ecosystem: pip
affected:
  - horovod <= 0.28.1
published: '2026-05-12'
updated: '2026-10-27'
sourceUpdated: '2026-10-27T16:45:03.541043960Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-mf8f-x4r3-jm8c'
references:
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-31234'
  - url: 'https://github.com/horovod/horovod'
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/horovod/PYSEC-2026-354.yaml
  - url: 'https://pypi.org/project/horovod'
  - url: 'https://www.notion.so/CVE-2026-31234-35d1e139318881d585cde508b9d2453c'
  - url: 'https://github.com/advisories/GHSA-mf8f-x4r3-jm8c'
tags:
  - osv
  - pip
  - ghsa
epss: 0.00687
epssPercentile: 0.52491
cwe:
  - CWE-502
ingestedAt: '2026-10-27T16:32:34.337Z'
---

## Overview

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.

## Affected packages

- `horovod <= 0.28.1`

## Remediation

Refer to the advisory for the patched release.