---
id: "CVE-2026-123838"
page: "https://infrastack.ai/live/CVE-2026-123838"
kind: "vulnerability"
aliases: ["CVE-2026-123838"]
title: "JetBrains IntelliJ IDEA: opening a UI Designer form runs code in Safe Mode"
severity: "high"
cvss: 7.8
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["intellij-idea", "java", "jetbrains", "kotlin", "runtime"]
not_affected_if: ["only-trusted-projects", "version-2026.3-or-later"]
published_at: "2026-11-06T17:17:22+00:00"
first_seen_at: "2026-11-06T17:43:12+00:00"
updated_at: "2026-11-06T17:45:00+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123838", "first_seen_at": "2026-11-06T17:43:12+00:00"}]
exploit_sources: []
---

# JetBrains IntelliJ IDEA: opening a UI Designer form runs code in Safe Mode

Link for people: https://infrastack.ai/live/CVE-2026-123838 (this .md is for agents)

In JetBrains IntelliJ IDEA before 2026.3, a crafted UI Designer form file could make the IDE execute code even while it was in Safe Mode. An attacker who gets a developer to open such a file in the IDE can run code as that developer.

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

## How to check

- Check the installed IntelliJ IDEA version under Help > About; versions before `2026.3` are in scope.

## Fix

- JetBrains IntelliJ IDEA: move to `2026.3` or later (per the sources' description: fixed in `2026.3`).

## Timeline

- 2026-11-06T17:43:12+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-123838

## From the sources

In JetBrains IntelliJ IDEA before 2026.3 code execution was possible in Safe Mode via UI Designer form file

---

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