Cross-site scripting in YouTrack - CVE-2026-100263
Published: October 2, 2026
Vulnerability identifier: #VU153142
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N]
CVE-ID: CVE-2026-100263
CWE-ID: CWE-79
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to inject arbitrary HTML content.
The vulnerability exists due to improper neutralization of user-controlled HTML in YouTrack when processing User-Agent headers. A remote attacker can send a request with a crafted User-Agent header to inject arbitrary HTML content.
Affected software
YouTrack
How to mitigate CVE-2026-100263
Install security update from vendor's website.
YouTrack - update to 2026.2.18991