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Vulnerability record

CVE-2026-126800

criticalCVSS 4.0 9.3Published · hydro-dev

The short answer

CVE-2026-126800 affects hydro-dev @hydrooj/ui-default and is rated critical (CVSS 9.3). It is not in CISA's Known Exploited Vulnerabilities catalog.

What it is

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.

Weakness: CWE-79.

Severity

9.3 critical

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Exploited (CISA KEV)

Not listed

CISA lists confirmed exploitation only

EPSS, next 30 days

No score

FIRST scores CVEs within a day of publication

How it can be exploited

Attack vector
Network
Attack complexity
Low
Attack requirements
None
Privileges required
Low
User interaction
Passive
Confidentiality impact
High
Integrity impact
High
Availability impact
None

Affected products

@hydrooj/ui-default. NVD's record lists the exact affected versions.

References

Questions

Is CVE-2026-126800 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog as of 2026-11-12.

How do I fix CVE-2026-126800?

Follow the vendor advisory in the references below. NVD lists the affected versions under its configurations.

From NVD, CISA KEV, FIRST EPSS and OSV.dev, checked . Status on NVD: Received. The description is NVD's text, quoted as published.

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