CVE-2026-77133: Frontend Profile Edit Privilege Escalation

CVE-2026-77133 Overview

CVE-2026-77133 is a missing authorization vulnerability [CWE-862] affecting a TYPO3 extension that provides a frontend profile edit plugin. The extension fails to restrict which frontend usergroups a logged-in user may assign to their own account when the profile edit plugin uses its default field configuration. An authenticated frontend user can escalate privileges by assigning themselves to arbitrary frontend usergroups. TYPO3 published this issue as Security Advisory SA-2026-024.

Critical Impact
Any authenticated frontend user can self-assign membership to arbitrary frontend usergroups, gaining access to protected content, pages, and functionality intended for privileged group members.

Affected Products

TYPO3 third-party extension providing the frontend profile edit plugin
Installations using the plugin's default field configuration
Refer to TYPO3 Security Advisory SA-2026-024 for specific affected versions

Discovery Timeline

2026-08-25 - CVE-2026-77133 published to NVD
2026-08-26 - Last updated in NVD database

Technical Details for CVE-2026-77133

Vulnerability Analysis

The vulnerability resides in the frontend profile edit plugin's handling of the usergroup field. When the plugin is rendered using its default field configuration, the usergroup property of the frontend user record is exposed as an editable form field without a server-side allow-list. A logged-in frontend user submits the profile edit form and includes crafted values for the usergroup field. The extension writes those values directly to the fe_users.usergroup column without validating whether the current user should be permitted to hold those groups.

The result is horizontal and vertical privilege escalation across the frontend authorization boundary. Access-restricted pages, plugin views, and content elements that depend on fe_group checks become reachable by any authenticated user.

Root Cause

The root cause is a missing authorization check [CWE-862] on a self-service write path. The extension trusts client-submitted values for a security-relevant field. TYPO3 core enforces usergroup restrictions on backend editing, but frontend plugins must implement their own allow-list. The default field configuration ships without one.

Attack Vector

Exploitation requires only a valid frontend user account and network access to the profile edit page. The attacker authenticates, loads the profile edit form, appends or modifies the usergroup input to reference a privileged frontend usergroup UID, and submits the form. No user interaction from an administrator is required. See the TYPO3 Security Advisory SA-2026-024 for vendor technical details.

// No verified exploit code is published.
// Refer to TYPO3 Security Advisory SA-2026-024 for technical details.

Detection Methods for CVE-2026-77133

Indicators of Compromise

Unexpected changes to the usergroup column of fe_users records that were not initiated by a backend editor.
Frontend user accounts with membership in administrative or premium-content usergroups that do not match business provisioning records.
Access log entries showing standard users retrieving pages or plugin views gated by fe_group restrictions.

Detection Strategies

Audit the fe_users table for accounts whose usergroup list changed after the vulnerable plugin was deployed, and reconcile against provisioning records.
Enable TYPO3 sys_history logging on fe_users writes and review entries where the actor is the frontend user themselves.
Inspect web server access logs for POST requests to the profile edit action that include a usergroup form parameter.

Monitoring Recommendations

Alert on any modification to fe_users.usergroup that originates from a frontend request rather than a backend user session.
Baseline the population of privileged frontend usergroups and alert on unexpected membership growth.
Forward TYPO3 application and web server logs to a centralized platform for correlation of authentication, profile-edit, and gated-content access events.

How to Mitigate CVE-2026-77133

Immediate Actions Required

Apply the fixed extension version referenced in TYPO3 Security Advisory SA-2026-024.
Review current fe_users.usergroup values and revert unauthorized memberships to a known-good state.
Rotate credentials and invalidate active sessions for any frontend account observed to have manipulated usergroup assignments.

Patch Information

Install the patched release of the affected TYPO3 extension as documented in TYPO3 Security Advisory SA-2026-024. The fix enforces a server-side allow-list on the usergroup field within the profile edit plugin so that submitted values are validated before being persisted to fe_users.

Workarounds

Override the plugin's default field configuration in TypoScript to remove usergroup from the editable fields list.
Restrict the profile edit plugin to trusted pages and add access checks that prevent group self-assignment.
Temporarily disable the profile edit plugin until the patched extension version is deployed.

bash

# TypoScript example: remove usergroup from the profile edit plugin's editable fields
# Adjust the extension key and plugin namespace to match your installation.
plugin.tx_<extkey>.settings.edit.fields := removeFromList(usergroup)