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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-18430
StatePUBLISHED
AssignerFluid Attacks
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-19 16:17:06 UTC
Updated2026-08-19 20:17:13 UTC
DescriptionHumHub 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.

Risk And Classification

Primary CVSS: v4.0 7.2 HIGH from [email protected]

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/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

EPSS: 0.003670000 probability, percentile 0.299890000 (date 2026-08-20)

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

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary7.2HIGHCVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:N/SC:L/SI:L/SA:N/E:X/C...
4.0CNACVSS7.2HIGHCVSS: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 v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
Present
Privileges Required
High
User Interaction
Passive
Confidentiality
High
Integrity
High
Availability
None
Sub Conf.
Low
Sub Integrity
Low
Sub Availability
None

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/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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA HumHub HumHub affected 1.18.4 Windows, MacOS, Linux

References

ReferenceSourceLinkTags
github.com/humhub/humhub/pull/8365 [email protected] github.com
fluidattacks.com/es/advisories/personajes 134c704f-9b21-4f2e-91b3-4a467353bcc0 fluidattacks.com
github.com/humhub/humhub [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Miguel Gomez (en)

CNA: Fluid Attacks' AI SAST Scanner (en)

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