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

> Remote attackers can achieve arbitrary code execution by injecting malicious pickle payloads into the unauthenticated KVStore HTTP server.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 12 May 2026
- **Updated:** 14 May 2026
- **Also known as:** GHSA-mf8f-x4r3-jm8c, PYSEC-2026-354

## What is CVE-2026-31234?

CVE-2026-31234 is a critical unsafe deserialization vulnerability in n/a, published on 12 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2026-31234?

3 open source packages ship an affected version, including horovod.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `horovod` | PyPI | All versions to 0.28.1 | None |
| `horovod` | PyPI | All versions to 0.28.1 | None |
| `horovod` | PyPI | All versions to 0.28.1 | None |

## How do I fix CVE-2026-31234?

No fix has been published for CVE-2026-31234 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-31234 being exploited?

There is no known exploitation of CVE-2026-31234 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31234 and fix it if it is affected.

What it is: CVE-2026-31234 is a critical unsafe deserialization vulnerability in n/a, published on 12 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-31234 in the wild and no public exploit code.

Affected packages and fixed versions:
- horovod (PyPI): affected all versions up to 0.28.1; no fix listed
- horovod (PyPI): affected all versions up to 0.28.1; no fix listed
- horovod (PyPI): affected all versions up to 0.28.1; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-31234/ (Markdown: https://insights.sbomify.com/CVE-2026-31234/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31234
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31234
- OSV: https://osv.dev/vulnerability/CVE-2026-31234

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31234/
Summaries are generated and may contain mistakes; the official description above is the record.