---
title: "CVE-2026-31220: PySyft server-side arbitrary Python execution after code approval"
url: https://erroneo.us/security/cve/CVE-2026-31220/
description: "CVE-2026-31220 (syft (PyPI)): PySyft (Syft Datasite/Server) versions 0.9.5 and earlier are vulnerable to remote code execution due to insufficient…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-05-12
date_modified: 2026-05-18
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-31220"
kev: false
cvss: 9.8
epss: 0.01198
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-31220: PySyft server-side arbitrary Python execution after code approval

**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 1.2% , percentile 68: FIRST’s model estimates a 1.2% chance of exploitation activity in the next 30 days, higher than 68% 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 syft (PyPI) <= 0.9.5, no fixed version listed . Check your lockfile, including transitive dependencies.

## What it is

PySyft (Syft Datasite/Server) versions 0.9.5 and earlier are vulnerable to remote code execution due to insufficient validation and sandboxing of user-submitted code. The system allows low-privileged users to submit Python functions (via @sy.syftfunction()) for remote execution on the server. While a code approval mechanism exists, the submitted code undergoes no security checks for dangerous operations (e.g., file access, command execution). Once approved, the code is executed within the server process using exec() and eval() functions without proper isolation. A remote attacker can leverage this to execute arbitrary Python code on the server, leading to complete compromise of the server environment.

## Affected packages

- PyPI `syft` <= 0.9.5 → 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): 1.20% probability of exploitation activity in the next 30 days; percentile 68.

## Sources

- [GitHub Advisory GHSA-cfpg-c974-jfhq](https://github.com/advisories/GHSA-cfpg-c974-jfhq)
- [CVE.org record CVE-2026-31220](https://www.cve.org/CVERecord?id=CVE-2026-31220)
- [NVD entry CVE-2026-31220](https://nvd.nist.gov/vuln/detail/CVE-2026-31220)
- [github.com](https://github.com/OpenMined/PySyft)
- [notion.so](https://www.notion.so/CVE-2026-31220-35d1e1393188814186b9e00114a8aba7)

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Source page: https://erroneo.us/security/cve/CVE-2026-31220/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt