Vulnpedia
← All CVEs

CVE-2026-18116

HIGH 7.3 ALL-YEARS

Published 2026-09-14 · Last modified 2026-09-15 · ConcreteCMS · NVD: Analyzed

Concrete CMS 8.3.0 to 9.5.2 stored calendar event names without sanitization and rendered them without HTML escaping in the workflow approval and deletion notifications shown in the dashboard "Waiting For Me" block. A registered user permitted to add events to a calendar governed by an approval workflow could submit an event whose name contained a script payload, which then executed in an administrator's browser when the pending request was displayed and could be used to create a new administrator account. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks v01demort for reporting.

ELEVATED IMPACT

Severe if exploited (CVSS 7.3), but no confirmed exploitation. Patch on a normal cadence.

Exploitation likelihood

0.2%chance of exploitation in 30 days · 4th percentile

○ In CISA KEV○ Public exploit / PoC◆ SSVC: exploitation none, automatable no

Impact if exploited

7.3CVSS 4.0 · HIGH · CNA

  • ConfidentialityHigh
  • IntegrityHigh
  • AvailabilityHigh

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ⚠Privileges: Requires an admin / high-privilege account
  • ⚠User interaction: Succeeds with passive user activity
  • ✓Complexity: No special conditions — reliably repeatable
  • ⚠Requirements: Specific conditions must be present

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept & exploit code

No public exploit or proof-of-concept code is catalogued for this CVE (no ExploitDB, Nuclei, or CISA-KEV entry). It may still exist — search GitHub or check the references below.

Affected

Vendors Concrete Cms Concretecms

Products Concrete Cms

Weakness (CWE)

  • CWE-79: Improper Neutralization of Input During Web Page Generation

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Known Affected Software Configurations

VendorProductVersion range
ConcretecmsConcrete Cms≥ 8.3.0 and < 9.5.3

All CVSS metrics

  • HIGH 7.3 v4.0 · CNA Primary
    CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
  • HIGH 7.3 v4.0 · NVD Secondary
    CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/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
  • MEDIUM 6.1 v3.1 · NVD Primary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

References

Patches & mitigations

Sources: NVD · CVE.org · EPSS