What is CVE-2026-100263?

CVE-2026-100263 is a medium-severity vulnerability in Jetbrains Youtrack, classified under Cross-site Scripting. CVSS score: 4.7/10. Published 2026-09-30.

How severe is CVE-2026-100263?

Medium severity. CVSS v3 base score is 4.7 out of 10.

XSS in Jetbrains Youtrack

CVE-2026-100263

In JetBrains YouTrack before 2026.2.18991 stored HTML injection via the User-Agent header was possible

Vulnerability class: XSS (Cross-Site Scripting)

Published 2026-09-30 · last modified 2026-09-30.

CVSS v3 metric

CVSS v3 base score 4.7 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Jetbrains Youtrack

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

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

Frequently asked questions

What is CVE-2026-100263?: CVE-2026-100263 is a medium-severity vulnerability in Jetbrains Youtrack, classified under Cross-site Scripting. CVSS score: 4.7/10. Published 2026-09-30.
How severe is CVE-2026-100263?: Medium severity. CVSS v3 base score is 4.7 out of 10.