CVE-2026-126800

HIGH 8.7

Hydro @hydrooj/ui-default before 4.59.1 Stored XSS via Markdown language- Class

CVSS Score

8.7

EPSS Score

0.0%

EPSS Percentile

0th

Hydro @hydrooj/ui-default before 4.59.1 contains a stored cross-site scripting vulnerability that allows registered users to inject script by placing double quotes in language- class tokens within markdown-it-xss.ts. Attackers can store a payload in their profile bio that executes when administrators or other users view it, stealing the non-httpOnly sid session cookie for session hijacking.

CWE	CWE-79
Vendor	hydro-dev
Product	@hydrooj/ui-default
Published	Nov 11, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Required

Scope

Changed

Confidentiality

High

Integrity

High

Availability

None

Affected Versions

hydro-dev / @hydrooj/ui-default

0 < 4.59.1

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/hydro-dev/Hydro/commit/3bae56fe8edddff12346bcb1c8281269c94688d8 github.com: https://github.com/hydro-dev/Hydro/blob/3c8286dd1350fcd00412e95d5b056dbfed64edda/packages/ui-default/backendlib/markdown-it-xss.ts#L150-L157 vul.yulun.ac.cn: https://vul.yulun.ac.cn/20261107/hydro/ vulncheck.com: https://www.vulncheck.com/advisories/hydro-hydrooj-ui-default-before-4.59.1-stored-xss-via-markdown-language-class

Credits

Wu Yulun