{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-18756", "assignerOrgId": "84fe0718-d6bb-4716-a7e8-81a6d1daa869", "state": "PUBLISHED", "assignerShortName": "Fluid Attacks", "dateReserved": "2026-08-04T01:50:20.595Z", "datePublished": "2026-08-19T14:46:25.019Z", "dateUpdated": "2026-08-19T14:46:25.019Z"}, "containers": {"cna": {"affected": [{"defaultStatus": "unaffected", "platforms": ["Windows", "MacOS", "Linux"], "product": "HumHub", "repo": "https://github.com/humhub/humhub", "vendor": "HumHub", "versions": [{"status": "affected", "version": "1.18.4"}]}], "cpeApplicability": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:humhub:humhub:1.18.4:*:windows:*:*:*:*:*", "vulnerable": true}, {"criteria": "cpe:2.3:a:humhub:humhub:1.18.4:*:macos:*:*:*:*:*", "vulnerable": true}, {"criteria": "cpe:2.3:a:humhub:humhub:1.18.4:*:linux:*:*:*:*:*", "vulnerable": true}], "negate": false, "operator": "OR"}], "operator": "OR"}], "credits": [{"lang": "en", "type": "finder", "value": "Miguel Gomez"}, {"lang": "en", "type": "finder", "value": "Fluid Attacks' AI SAST Scanner"}], "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<span style=\"background-color: rgb(255, 255, 255);\">HumHub 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 </span><code>options</code><span style=\"background-color: rgb(255, 255, 255);\"> query-string parameter of </span><code>space/membership/request-membership-form</code><span style=\"background-color: rgb(255, 255, 255);\">, lure an authenticated non-member into submitting the legitimate membership request form, and cause the server to return JavaScript containing attacker-controlled code.</span><br>"}], "value": "HumHub 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."}], "impacts": [{"capecId": "CAPEC-591", "descriptions": [{"lang": "en", "value": "CAPEC-591 Reflected XSS"}]}], "metrics": [{"cvssV4_0": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "baseScore": 7.2, "baseSeverity": "HIGH", "privilegesRequired": "LOW", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "LOW", "subIntegrityImpact": "LOW", "userInteraction": "ACTIVE", "valueDensity": "NOT_DEFINED", "vectorString": "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", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"cweId": "CWE-79", "description": "CWE-79 Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting')", "lang": "en", "type": "CWE"}]}], "providerMetadata": {"orgId": "84fe0718-d6bb-4716-a7e8-81a6d1daa869", "shortName": "Fluid Attacks", "dateUpdated": "2026-08-19T14:46:25.019Z"}, "references": [{"tags": ["third-party-advisory"], "url": "https://fluidattacks.com/es/advisories/turizo"}, {"tags": ["product"], "url": "https://github.com/humhub/humhub"}, {"tags": ["patch"], "url": "https://github.com/humhub/humhub/pull/8381"}], "source": {"discovery": "UNKNOWN"}, "title": "HumHub Community Edition 1.18.4-pl1 - Reflected XSS in Space membership request button rendering", "x_generator": {"engine": "Vulnogram 0.2.0"}}}}

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{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "platforms": ["Windows", "MacOS", "Linux"], "product": "HumHub", "repo": "https://github.com/humhub/humhub", "vendor": "HumHub", "versions": [{"status": "affected", "version": "1.18.4"}]}], "source": "help@fluidattacks.com"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "HumHub 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."}], "id": "CVE-2026-18756", "lastModified": "2026-08-19T15:16:58.150", "metrics": {"cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 7.2, "baseSeverity": "HIGH", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "LOW", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "LOW", "subIntegrityImpact": "LOW", "userInteraction": "ACTIVE", "valueDensity": "NOT_DEFINED", "vectorString": "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", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "help@fluidattacks.com", "type": "Secondary"}]}, "published": "2026-08-19T15:16:58.150", "references": [{"source": "help@fluidattacks.com", "url": "https://fluidattacks.com/es/advisories/turizo"}, {"source": "help@fluidattacks.com", "url": "https://github.com/humhub/humhub"}, {"source": "help@fluidattacks.com", "url": "https://github.com/humhub/humhub/pull/8381"}], "sourceIdentifier": "help@fluidattacks.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-79"}], "source": "help@fluidattacks.com", "type": "Primary"}]}

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