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Concrete Cms EUVDEUVD-2026-78913

| CVE-2026-18115 HIGH
Missing Authorization (CWE-862)
2026-09-15 ConcreteCMS GHSA-j7cg-26vv-9hjf
Authentication Bypass Concrete Cms
7.4
CVSS 4.0 · Vendor: ConcreteCMS
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Vulnerability Assessment

Weakness
CWE
CWE-862
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Authorization checks on every request
MITRE ATT&CK

1 technique across 1 tactic: Privilege Escalation

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
No patch listed yet 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 15, 2026

Account takeover of non-superuser accounts is possible in Concrete CMS 9.2.0 through 9.5.2 because the REST API user write endpoints (PUT /ccm/api/1.0/users/{uID} and POST /ccm/api/1.0/users/{uID}/change_password) fail to enforce per-field edit_user_properties permissions. An attacker holding an OAuth token scoped for updates and permission to edit only one non-sensitive field on another user can rewrite that user's password, username, email, and attributes, fully seizing the account; superuser accounts are explicitly out of reach. There is no public exploit identified and no CISA KEV listing at time of analysis, so this currently represents a targeted, credential-gated authorization defect rather than a mass-exploitation event. Concrete CMS rated it CVSS v4.0 7.4 (CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:N).

Affected VersionsENISA

Concrete CMS 9.2.0 ≤9.5.2

Affected Packages

euvd concrete_cms no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

Vendor (ConcreteCMS) PRIMARY 7.4 HIGH
CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (ConcreteCMS) · only source for this CVE.

CVSS VectorVendor: ConcreteCMS

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
Present
Privileges Required
High
User Interaction
None
Vulnerable system: Confidentiality
High
Vulnerable system: Integrity
High
Vulnerable system: Availability
None
Subsequent system: Confidentiality
None
Subsequent system: Integrity
None
Subsequent system: Availability
None

DescriptionCVE.org

Concrete CMS 9.2.0 to 9.5.2 did not enforce per-field edit_user_properties permissions on the REST API user write endpoints (PUT /ccm/api/1.0/users/{uID} and POST /ccm/api/1.0/users/{uID}/change_password). A user with an update-scoped OAuth token and permission to edit only one non-sensitive field could change another non-superuser's password, username, email, and attributes, taking over that account. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.4 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N. Thanks riodrwn for reporting.

Threat Intelligence Overview

EPSS Score
0.2%
Top 86% exploitable
Data Quality
5 sources
Confidence: Medium
EUVD NVD CVE.org EPSS Vulnrichment

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.2%
Patch available No
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
No
Human Impact· derived
Medium
Technical Impact
Total

Priority Score

37
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +37
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication Bypass CRITICAL

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

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Same technique Authentication Bypass

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References

Advisories & patches
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-18115 REF https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes

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