CVE-2026-18430 PUBLISHED

HumHub 1.18.4 - Stored XSS in comment-deletion notifications through unescaped administrator reason

Assigner: Fluid Attacks
Reserved: 30.07.2026 Published: 19.08.2026 Updated: 19.08.2026

HumHub 1.18.4 contains a stored cross-site scripting vulnerability in the comment-deletion notification flow. A Space administrator can delete another user's comment, choose to notify the original author, and place HTML/JavaScript in the deletion reason.

Metrics

CVSS 4.0

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:N/SC:L/SI:L/SA:N
CVSS Score: 7.2

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	High	Confidentiality	Low
Attack Complexity	Low	Integrity	High	Integrity	Low
Attack Requirements	Present	Availability	None	Availability	None
Privileges Required	High
User Interaction	Passive

CVSS 4.0

Product Status

Vendor	HumHub
Product	HumHub
Versions	Default: unaffected Version 1.18.4 is affected

Credits

Miguel Gomez finder
Fluid Attacks' AI SAST Scanner finder

References

Problem Types

CWE-79 Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') CWE

Impacts

CAPEC-592 Stored XSS