Vulnerability · Published Aug 19, 2026 · Assigned by Fluid Attacks

CVE-2026-18756HumHub Community Edition 1.18.4-pl1 - Reflected XSS in Space membership request button rendering

High 7.2

In plain English

A high-severity cross-site scripting in HumHub from HumHub. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities).

Severity (CVSS 4.0)7.2High

Exploit odds (30 days)0.5%top 59.4% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
HumHub	HumHub	1.18.4

Weakness: CWE-79 · Vector: 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

References

https://fluidattacks.com/es/advisories/turizo third-party-advisory
https://github.com/humhub/humhub product
https://github.com/humhub/humhub/pull/8381 patch