What is CVE-2026-123309?

CVE-2026-123309 is a medium-severity vulnerability in Jetbrains Intellij Idea, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-11-06.

How severe is CVE-2026-123309?

Medium severity. CVSS v3 base score is 6.1 out of 10.

XSS in Jetbrains Intellij Idea

CVE-2026-123309

In JetBrains IntelliJ IDEA before 2026.3, 2026.2.4 stored XSS was possible on the built-in web server via Markdown preview

Vulnerability class: XSS (Cross-Site Scripting)

Published 2026-11-06 · last modified 2026-11-06.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.002 (13.9th percentile), scored 2026-11-09.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 14th percentile — 13.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

The 30-day trend appears once there are two daily scores.

Affected products

Jetbrains Intellij Idea

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

www.jetbrains.com/privacy-security/issues-fixed/

Frequently asked questions

What is CVE-2026-123309?: CVE-2026-123309 is a medium-severity vulnerability in Jetbrains Intellij Idea, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-11-06.
How severe is CVE-2026-123309?: Medium severity. CVSS v3 base score is 6.1 out of 10.