---
id: "CVE-2026-123854"
page: "https://infrastack.ai/live/CVE-2026-123854"
kind: "vulnerability"
aliases: ["CVE-2026-123854"]
title: "JetBrains PyCharm: crafted Jupyter notebook runs code even in Safe Mode"
severity: "medium"
cvss: 5.5
epss: null
exploited: false
status: "open"
category: "other"
products: []
ecosystems: []
tags: ["jupyter", "other", "pycharm", "python"]
not_affected_if: ["pycharm-2026.3-or-later"]
published_at: "2026-11-06T17:17:24+00:00"
first_seen_at: "2026-11-06T17:43:13+00:00"
updated_at: "2026-11-06T17:45:21+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123854", "first_seen_at": "2026-11-06T17:43:13+00:00"}]
exploit_sources: []
---

# JetBrains PyCharm: crafted Jupyter notebook runs code even in Safe Mode

Link for people: https://infrastack.ai/live/CVE-2026-123854 (this .md is for agents)

Before PyCharm 2026.3, a crafted Jupyter notebook widget module could execute code while PyCharm was in Safe Mode. An attacker who gets a developer to open such a notebook can run code on that developer's machine.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed PyCharm version under Help > About
- Compare it with `2026.3`; anything earlier is in the affected range

## Fix

- JetBrains PyCharm: upgrade to `2026.3` or later

## Timeline

- 2026-11-06T17:43:13+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-123854

## From the sources

In JetBrains PyCharm before 2026.3 code execution was possible in Safe Mode via a crafted Jupyter notebook widget module

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_