---
title: "CVE-2026-31234: Horovod contains an insecure deserialization vulnerability in its KVStore HTTP server component"
url: https://erroneo.us/security/cve/CVE-2026-31234/
description: "CVE-2026-31234 (horovod (PyPI)): Horovod thru 0.28.1 contains an insecure deserialization vulnerability (CWE-502) in its KVStore HTTP server component. The…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-05-12
date_modified: 2026-05-27
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-31234"
kev: false
cvss: 9.8
epss: 0.01031
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-31234: Horovod contains an insecure deserialization vulnerability in its KVStore HTTP server component

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 1.0% , percentile 63: FIRST’s model estimates a 1.0% chance of exploitation activity in the next 30 days, higher than 63% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes horovod (PyPI) <= 0.28.1, no fixed version listed . Check your lockfile, including transitive dependencies.

## What it is

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

- PyPI `horovod` <= 0.28.1 → fixed: none listed

## Affected products (CVE record)

- n/a n/a: see advisory

## Severity

- CISA-ADP CVSS 3.1: 9.8 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`
- GitHub CVSS 3.1: 9.8 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 1.03% probability of exploitation activity in the next 30 days; percentile 63.

## Sources

- [GitHub Advisory GHSA-mf8f-x4r3-jm8c](https://github.com/advisories/GHSA-mf8f-x4r3-jm8c)
- [CVE.org record CVE-2026-31234](https://www.cve.org/CVERecord?id=CVE-2026-31234)
- [NVD entry CVE-2026-31234](https://nvd.nist.gov/vuln/detail/CVE-2026-31234)
- [github.com](https://github.com/horovod/horovod)
- [notion.so](https://www.notion.so/CVE-2026-31234-35d1e139318881d585cde508b9d2453c)

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Source page: https://erroneo.us/security/cve/CVE-2026-31234/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt