CVE-2026-18756

HIGHPre-NVD 7.27.2—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.2 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 73% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
7.2EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.2Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 v3
7.2
EG Score
7.2(medium)
EG Risk
33(Track)
EG Risk 33/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity72% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
27%
KEV
Not listed

Published

August 19, 2026

Last Modified

August 28, 2026

Advisory Details (3)

Auto-updated Aug 19, 2026
Patch available. Sources: github_pr.
github_pr Patch Available

Limit request supplied membership and friendship button options to presentation values

Patch available: humhub/humhub v1.18.5 (PR #8381 merged 2026-08-17)

https://github.com/humhub/humhub/pull/8381
generic

GitHub - humhub/humhub: HumHub is an Open Source Enterprise Social Network. Easy to install, intuitive to use and extendable with countless freely available modules. · GitHub

https://github.com/humhub/humhub
generic

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

https://fluidattacks.com/es/advisories/turizo

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 11× in last 7d / 20× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-30 01:22 UTCEPSS rescore
  2. 2026-08-29 04:33 UTCEG score recompute
  3. 2026-08-28 21:41 UTCEPSS rescore
  4. 2026-08-27 20:04 UTCEG score recompute
  5. 2026-08-27 14:25 UTCEPSS rescore
  6. 2026-08-26 19:36 UTCEG score recompute
  7. 2026-08-26 14:46 UTCEPSS rescore
  8. 2026-08-25 19:08 UTCEG score recompute
  9. 2026-08-25 13:48 UTCEPSS rescore
  10. 2026-08-24 18:41 UTCEG score recompute
  11. 2026-08-23 06:02 UTCEG score recompute
  12. 2026-08-23 00:19 UTCEPSS rescore
  13. 2026-08-22 05:35 UTCEG score recompute
  14. 2026-08-21 23:49 UTCEPSS rescore
  15. 2026-08-21 17:22 UTCEG score recompute
  16. 2026-08-21 04:04 UTCEG score recompute
  17. 2026-08-20 22:55 UTCEPSS rescore
  18. 2026-08-19 15:24 UTCEG score recompute
  19. 2026-08-19 14:57 UTCEG score recompute
  20. 2026-08-19 14:57 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-18756?
CVE-2026-18756 is a high vulnerability published on August 19, 2026. 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…
When was CVE-2026-18756 disclosed?
CVE-2026-18756 was first published in the National Vulnerability Database on August 19, 2026, with the most recent update on August 28, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-18756 actively exploited?
CVE-2026-18756 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 73.1% of all scored CVEs.
What is the CVSS score of CVE-2026-18756?
CVE-2026-18756 has a CVSS v3 base score of 7.2 (NVD).
How do I remediate CVE-2026-18756?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-18756, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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