HumHub Community Edition 1.18.4-pl1 - Reflected XSS in Space membership request button rendering

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-18756
StatePUBLISHED
AssignerFluid Attacks
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-19 15:16:58 UTC
Updated2026-08-21 17:16:30 UTC
DescriptionHumHub Community Edition 1.18.4 contains a reflected cross-site scripting vulnerability in the Space membership-request workflow. An attacker can place attacker-controlled button configuration in the options query-string parameter of space/membership/request-membership-form, lure an authenticated non-member into submitting the legitimate membership request form, and cause the server to return JavaScript containing attacker-controlled code.

Risk And Classification

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

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:A/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: 0.003430000 probability, percentile 0.267810000 (date 2026-08-24)

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:L/UI:A/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:L/UI:A/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
Low
User Interaction
Active
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:L/UI:A/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/8381 [email protected] github.com
fluidattacks.com/es/advisories/turizo [email protected] 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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