# CVE-2026-31234: Horovod insecure deserialization in KVStore HTTP server

Source: https://junglewise.ai/threats/cve-2026-31234-horovod-insecure-deserialization-in-kvstore-http-server  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-12. Updated: 2026-05-27  
License: CC BY 4.0 with a link back

CVE-2026-31234 · Severity: critical · CVSS 9.8 · Published 2026-05-12

Horovod is a distributed training framework used to speed up deep learning tasks across multiple computers. A security flaw in its coordination component allows an attacker to send malicious data that, when processed by the system, results in full remote control over the affected servers. This could lead to the theft of sensitive AI models, data breaches, or complete disruption of research and development operations.

Technologies: [horovod (PyPI)](https://junglewise.ai/threats/technologies/pypi-horovod). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-31234 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-31234 being exploited in the wild.

**How severe is CVE-2026-31234?** Critical severity, with a CVSS score of 9.8, published 12 May 2026.

**Which products and versions are affected?** Horovod <= 0.28.1, up to and including 0.28.1; horovod (PyPI) ECOSYSTEM:introduced=0,last_affected=0.28.1.

**Is there a fix for CVE-2026-31234?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-31234 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-31234?** Check whether you run Horovod or horovod (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

Horovod through version 0.28.1 is vulnerable to insecure deserialization (CWE-502) within its KVStore HTTP server component. The KVStore server, which facilitates distributed task coordination, lacks authentication and authorization, permitting unauthenticated remote attackers to submit arbitrary data via HTTP PUT requests. When a Horovod worker subsequently retrieves this data via HTTP GET, it processes the payload using cloudpickle.loads() without integrity verification. By injecting a malicious pickle payload, an attacker can achieve arbitrary code execution on the worker nodes. As of the advisory date, no patched versions have been identified.

## Affected products

- horovod horovod <= 0.28.1

## Identifiers

- CVE-2026-31234
- GHSA-mf8f-x4r3-jm8c
- PYSEC-2026-354

## Timeline

- 2026-05-12: disclosed
- 2026-05-12: advisory

## References

- [https://github.com/horovod/horovod](https://github.com/horovod/horovod)
- [https://www.notion.so/CVE-2026-31234-35d1e139318881d585cde508b9d2453c](https://www.notion.so/CVE-2026-31234-35d1e139318881d585cde508b9d2453c)

## Related threats

- [Horovod Vulnerable to Command Injection](https://junglewise.ai/threats/cve-2024-10190-horovod-vulnerable-to-command-injection)
- [PYSEC-2022-175 - Insecure Temporary File in GitHub repository horovod/horovod prior to 0.24.0.](https://junglewise.ai/threats/cve-2022-0315-use-of-insecure-temporary-file-in-horovod)