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Vulnerability record · CVE-2026-18756 · published 19 August 2026

CVE-2026-18756: Cross-site scripting vulnerability

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.

7.2 CVSS 4.0 High EPSS 0.47% · top 62.0% CWE-79 · Cross-site scripting Deferred
7.2CVSS 4.0 base score
0.47%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
28 Aug 2026Last modified by NVD

Description

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.

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:

References

LinkTags
https://fluidattacks.com/es/advisories/turizo
https://github.com/humhub/humhub
https://github.com/humhub/humhub/pull/8381

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Source: NIST National Vulnerability Database (record CVE-2026-18756), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.