| Package | Affected versions | Patched versions |
|---|---|---|
| craftcms/cms | ≥ 4.0.0-RC1, < 4.17.6≥ 5.0.0-RC1, < 5.9.12 | 4.17.65.9.12 |
| craft cms | = 4.0.0= 5.0.0≥ 4.0.0.1, < 4.17.6≥ 5.0.1, < 5.9.12 | 4.17.65.9.12 |
A low-privilege user (or an unauthenticated user who has been sent a shared URL) can escalate their privileges to admin by abusing UsersController->actionImpersonateWithToken.
Affected users should update to Craft 4.17.6 and 5.9.12 to mitigate the issue.
This vulnerability allows any low-privilege user to escalate their privileges and become an admin, or, in extreme circumstances, unprivileged users to do the same.
Therefore, this vulnerability affects Craft Pro and Team more than Craft Solo.
Specifically, an attacker who possesses a valid “preview token” can then append &action=users/impersonate-with-token&userId=1&prevUserId=1 to the preview URL to hijack the request into the impersonation endpoint, logging in as any user (including admin) without authentication. Getting the preview token is easy, and all an editor would have to do is create a single article, click “Preview”, and then recover this token.
Here’s what happens:
actionPreview() passes $skipSpecialHandling=true to handleRequest(), bypassing all security guards, and passes $checkToken=false to checkIfActionRequest(), which allows an attacker-controlled action query parameter to override the dispatch target.requireToken() guard on actionImpersonateWithToken() only checks a boolean (_hadToken) that was set when the preview token was initially resolved. It does not verify that the token was intended for the impersonation action, and so any valid token from any route satisfies the check.actionImpersonateWithToken is listed in $allowAnonymous and performs no authorization beyond requireToken(), so no prior authentication is required.The PoC achieves full admin takeover on the latest Craft CMS 5.9.10. Spawn a local version of Craft. Then, you’ll want to log in and create a valid setup:
Next, obtain a preview token
http://host:18895/blog/title?x-craft-live-preview=...&token=XXXXXXXXtoken= valueFinally, execute the exploit:
1. Open a new incognito/private browser window
2. Navigate to: http://host:18895/?token=XXXXXXXX&action=users/impersonate-with-token&userId=1&prevUserId=1
3. You may see a 404. This is expected.
To verify the exploit, in the same incognito tab, navigate to http://host:18895/admin. You should land on the admin dashboard, logged in as admin, without ever entering credentials.
Privilege escalation; everyone is impacted.
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