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CVE-2026-18426
2.0 LOW
- CVSS version (CVSS): 4.0
- Attack Vector (AV): Network (N)
- Attack Complexity (AC): High (H)
- Attack Requirement (AT): Present (P)
- Privileges Required (PR): High (H)
- User Interaction (UI): Passive (P)
- Vulnerable System Impact Confidentiality (VC): Low (L)
- Vulnerable System Impact Integrity (VI): None (N)
- Vulnerable System Impact Availability (VA): None (N)
- Subsequent System Impact Confidentiality (SC): None (N)
- Subsequent System Impact Integrity (SI): None (N)
- Subsequent System Impact Availability (SA): None (N)
- Modified Attack Vector (MAV): Network (N)
- Modified Attack Complexity (MAC): High (H)
- Modified Attack Requirement (MAT): Present (P)
- Modified Privileges Required (MPR): High (H)
- Modified User Interaction (MUI): Passive (P)
- Modified Vulnerable System Impact Confidentiality (MVC): Low (L)
- Modified Vulnerable System Impact Integrity (MVI): None (N)
- Modified Vulnerable System Impact Availability (MVA): None (N)
- Modified Subsequent System Impact Confidentiality (MSC): Negligible (N)
- Modified Subsequent System Impact Integrity (MSI): Negligible (N)
- Modified Subsequent System Impact Availability (MSA): Negligible (N)
- Safety (S): Not Defined (X)
- Automatable (AU): Not Defined (X)
- Recovery (R): Not Defined (X)
- Value Density (V): Not Defined (X)
- Vulnerability Response Effort (RE): Not Defined (X)
- Provider Urgency (U): Not Defined (X)
- Confidentiality Req. (CR): Not Defined (X)
- Integrity Req. (IR): Not Defined (X)
- Availability Req. (AR): Not Defined (X)
- Exploit Maturity (E): Not Defined (X)
Activity log
- Created & dismissed (no matching packages found) suggestion
Concrete CMS 9.0.0 to 9.5.2 Express Form block missing authorization allows an authenticated editor to modify Express Forms they cannot edit
Concrete CMS 9.0.0 through 9.5.2 did not enforce a block-level edit-permission check on the Express Form block's control-management actions, which relied solely on CSRF token validation. Because the token is bound to the user and action rather than to a specific block, page, or form, an authenticated user with edit access to one Express Form could reuse a validly obtained token to add, modify, or delete controls on Express Forms they were not authorized to edit, including injecting a control whose value is later rendered as HTML to achieve stored XSS. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 2.0 with vector CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Yat Wu for reporting.
References
Affected products
Concrete CMS
- =<9.5.2