GHSA-2xfc-g69j-x2mp CVE-2026-28781
Craft CMS: Entries Authorship Spoofing via Mass Assignment
- Severity
- 0.0 / 10
- Medium · CVSS 4.0
- Exploit chance (EPSS)
- 0.39%
- Chance of exploitation in the next 30 days. Higher than 32.89% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-639 Authorization Bypass Through User-Controlled Key
- CWE-915 Improperly Controlled Modification of Dynamically-Determined Object Attributes
- Fix
5.9.0-beta.1- Upgrade craftcms/cms to this version or later
Description
Description
The entry creation process allows for Mass Assignment of the authorId attribute. A user with "Create Entries" permission can inject the authorIds[] (or authorId) parameter into the POST request, which the backend processes without verifying if the current user is authorized to assign authorship to others.
Normally, this field is not present in the request for users without the necessary permissions. By manually adding this parameter, an attacker can attribute the new entry to any user, including Admins. This effectively "spoofs" the authorship.
Proof of Concept
Prerequisites
- A user account with "Create Entries" permission for a section.
- Victim's account ID (e.g.,
1for the default Admin).
Steps to Reproduce
- Log in as the attacker
- Navigate to the "Entries" section and click "New Entry"
- Fill in the required fields
- Enable a proxy tool (e.g., Burp Suite) to intercept requests
- Click "Save" & Intercept the request
- In the request body, add a new parameter to the body params:
&authorIds[]=<Victim_ID> - Forward the request
- Log in as an admin / as with the victim account
- Go to entries & Observe the newly created entry is listed and the author is the victim account, not the actual creator
Impact
- A user can create entries that appear to belong to higher-privileged users, potentially bypassing review processes or gaining trust based on false authorship.
- An attacker could post malicious or inappropriate content attributed to an administrator or other trusted users.
Resources
https://github.com/craftcms/cms/commit/c6dcbdffaf6ab3ffe77d317336684d83699f4542 https://github.com/craftcms/cms/commit/830b403870cd784b47ae42a3f5a16e7ac2d7f5a8
Affected versions
Packagist
| Package | Vulnerable | Fixed in |
|---|---|---|
| craftcms/cms | >= 5.0.0-RC1, < 5.9.0-beta.1 |
5.9.0-beta.1 |
| craftcms/cms | >= 4.0.0-RC1, < 4.17.0-beta.1 |
4.17.0-beta.1 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
craftcms/cms Packagist → 5.9.0-beta.1
- composer
composer require craftcms/cms:^5.9.0-beta.1
Severity breakdown
CVSS 4.0 0.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- None
- Privileges required
- Low
- User interaction
- None
- Confidentiality (vulnerable system)
- None
- Integrity (vulnerable system)
- High
- Availability (vulnerable system)
- None
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
- Exploit maturity
- Proof of concept
CVSS 3.1 6.5
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- None
Weakness
CWE-639: Authorization Bypass Through User-Controlled Key
The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.
How to prevent it
- Architecture and Design: For each and every data access, ensure that the user has sufficient privilege to access the record that is being requested.
- Architecture and Design, Implementation: Make sure that the key that is used in the lookup of a specific user's record is not controllable externally by the user or that any tampering can be detected.
- Architecture and Design: Use encryption in order to make it more difficult to guess other legitimate values of the key or associate a digital signature with the key so that the server can verify that there has been no tampering.
CWE-915: Improperly Controlled Modification of Dynamically-Determined Object Attributes
The product receives input from an upstream component that specifies multiple attributes, properties, or fields that are to be initialized or updated in an object, but it does not properly control which attributes can be modified.
How to prevent it
- Implementation: If available, use features of the language or framework that allow specification of allowlists of attributes or fields that are allowed to be modified. If possible, prefer allowlists over denylists. For applications written with Ruby on Rails, use the attr_accessible (allowlist) or attr_protected (denylist) macros in each class that may be used in mass assignment.
- Architecture and Design, Implementation: If available, use the signing/sealing features of the programming language to assure that deserialized data has not been tainted. For example, a hash-based message authentication code (HMAC) could be used to ensure that data has not been modified.
- Implementation: For any externally-influenced input, check the input against an allowlist of internal object attributes or fields that are allowed to be modified.
- Implementation, Architecture and Design: Refactor the code so that object attributes or fields do not need to be dynamically identified, and only expose getter/setter functionality for the intended attributes.
References
Advisories
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-7vrx-9684-xrf2 Craft CMS stores arbitrary content provided by unauthenticated users in session files | Medium Known exploited | Also affects craftcms/cms |
| GHSA-f3gw-9ww9-jmc3 Craft CMS Allows Remote Code Execution | Critical Known exploited | Also affects craftcms/cms |
| GHSA-x684-96hh-833x Craft CMS has a potential RCE with a compromised security key | High Known exploited | Also affects craftcms/cms |
| GHSA-2p6p-9rc9-62j9 Craft CMS has potential RCE when PHP `register_argc_argv` config setting is enabled | Critical Known exploited | Also affects craftcms/cms |
| GHSA-wg23-69c2-gjc8 Craft CMS: Passkey login accepts replayed WebAuthn assertions | Medium | Also affects craftcms/cms |
| GHSA-957r-qf9p-67xw Craft CMS: Arbitrary file read via SplFileObject in non-sandboxed template contexts | Medium | Also affects craftcms/cms |
| GHSA-596p-6jv8-775v Craft CMS: Authenticated leak of secret environment variables | Medium | Also affects craftcms/cms |
| GHSA-xxpx-f366-4xpq Craft CMS: Authorization bypass: view-only Categories user can modify category structure via structures/move-element | Medium | Also affects craftcms/cms |
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