Cross-site scripting in IntelliJ IDEA - CVE-2026-123309
Published: November 6, 2026
Vulnerability identifier: #VU159683
CSH Severity: Medium
CVSS v4: 5.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N]
CVE-ID: CVE-2026-123309
CWE-ID: CWE-79
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to execute arbitrary script in a victim's browser in the context of the built-in web server.
The vulnerability exists due to improper neutralization of stored content in IntelliJ IDEA's built-in web server Markdown preview when rendering Markdown content. A remote attacker can inject malicious script into content displayed in the preview to execute arbitrary script when a victim views that content.
Affected software
IntelliJ IDEA
How to mitigate CVE-2026-123309
Install security update from vendor's website.
IntelliJ IDEA - addressed in versions 2026.2.4, 2026.3