---
id: "CVE-2026-123850"
page: "https://infrastack.ai/live/CVE-2026-123850"
kind: "vulnerability"
aliases: ["CVE-2026-123850"]
title: "JetBrains YouTrack: CSS injection through Mermaid diagram configuration directives"
severity: "low"
cvss: 3.5
epss: null
exploited: false
status: "open"
category: "vendor"
products: []
ecosystems: []
tags: ["jetbrains", "self-hosted", "vendor", "youtrack"]
not_affected_if: ["mermaid-diagrams-unused", "youtrack-cloud"]
published_at: "2026-11-06T17:17:24+00:00"
first_seen_at: "2026-11-06T17:43:13+00:00"
updated_at: "2026-11-06T17:45:44+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123850", "first_seen_at": "2026-11-06T17:43:13+00:00"}]
exploit_sources: []
---

# JetBrains YouTrack: CSS injection through Mermaid diagram configuration directives

Link for people: https://infrastack.ai/live/CVE-2026-123850 (this .md is for agents)

Before version 2026.2.19422, YouTrack let CSS be injected into Mermaid diagrams through configuration directives. An attacker who can get a crafted diagram rendered could alter how the page looks, with limited impact beyond that.

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

## How to check

- Check the YouTrack version in the admin settings or About page; versions before `2026.2.19422` are affected.

## Fix

- YouTrack: move to `2026.2.19422` or later.

## Timeline

- 2026-11-06T17:43:13+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-123850

## From the sources

In JetBrains YouTrack before 2026.2.19422 cSS injection was possible in Mermaid diagrams via configuration directives

---

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