CVE-2026-31234: Horovod Horovod Contains An Insecure Deserialization Vulnerability

CRITICAL
Advisory Identifier: GHSA-mf8f-x4r3-jm8c
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CVSS 9.8
CWE-502
Published
Advisory Summary

CVE-2026-31234 is a CRITICAL (CVSS 9.8) horovod contains an insecure deserialization vulnerability (CWE-502: Deserialization of Untrusted Data) affecting Horovod libraries in the PyPI ecosystem. The issue involves horovod contains an insecure deserialization vulnerability in its kvstore http server component. Remediation is available in the latest vendor maintenance releases.

CVE-2026-31234 at a Glance

CVE Identifier CVE-2026-31234
GHSA Identifier GHSA-mf8f-x4r3-jm8c
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-502: Deserialization of Untrusted Data
Affected Product Horovod
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 9.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2026-31234

To remediate this vulnerability, upgrade all affected Horovod dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

horovod fixed: Latest secure release 
pip install horovod>=Latest secure release
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show horovod

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-31234, inspect your installed packages using pip:

pip show horovod

Analyze the terminal output to locate any version of Horovod in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The pip show horovod command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-502: Deserialization of Untrusted Data, where the product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid. In Horovod, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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.

CVE-2026-31234 Affected Horovod Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
horovod
pypi/horovod
PyPI
≤ 0.28.1

References

NVD — CVE-2026-31234 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-31234
Horovod Source Repository REPOSITORY
https://github.com/horovod/horovod
www.notion.so/cve-2026-31234-35d1... WEB
https://www.notion.so/CVE-2026-31234-35d1e139318881d585cde508b9d2453c

Frequently Asked Questions

What is CVE-2026-31234?
CVE-2026-31234 is a security vulnerability in Horovod involving Horovod contains an insecure deserialization vulnerability in its KVStore HTTP server component under CWE-502: Deserialization of Untrusted Data.
Which Horovod versions are affected?
Affected versions include releases prior to current release patches across affected packages: horovod.
What version fixes CVE-2026-31234?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is horovod affected?
Yes, horovod is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of CVE-2026-31234?
CVE-2026-31234 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-31234?
CVE-2026-31234 is classified under CWE-502: Deserialization of Untrusted Data (The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.).
How can I check PyPI dependencies for CVE-2026-31234?
Run the dependency tree command: 'pip show horovod'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-mf8f-x4r3-jm8c",
  "modified" : "2026-05-27T21:45:19Z",
  "published" : "2026-05-12T18:30:40Z",
  "aliases" : [ "CVE-2026-31234" ],
  "summary" : "Horovod contains an insecure deserialization vulnerability in its KVStore HTTP server component",
  "details" : "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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "horovod"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "0.28.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-31234"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/horovod/horovod"
  }, {
    "type" : "WEB",
    "url" : "https://www.notion.so/CVE-2026-31234-35d1e139318881d585cde508b9d2453c"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-502" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-27T21:45:19Z",
    "nvd_published_at" : "2026-05-12T18:16:51Z"
  }
}