CVE-2026-77141: Club Extension Auth Bypass Vulnerability

CVE-2026-77141 Overview

CVE-2026-77141 is an Insecure Direct Object Reference (IDOR) vulnerability in a TYPO3 extension that manages club records. The extension resolves the target record from a user-supplied request argument in its frontend edit, update, and activate actions. None of these actions perform an ownership check on the resolved record. An unauthenticated attacker who knows the UID of a club record can send a direct request to the update or activate action. The attacker can overwrite arbitrary records or publish records still awaiting approval. The issue is tracked under CWE-639: Authorization Bypass Through User-Controlled Key.

Critical Impact
Unauthenticated attackers can tamper with any club record or bypass moderation by activating pending records, provided they know or can guess a record UID.

Affected Products

TYPO3 third-party extension referenced in TYPO3 Security Advisory #2026-019
Frontend edit, update, and activate actions of the affected extension
TYPO3 installations exposing the vulnerable extension's frontend plugin

Discovery Timeline

2026-08-25 - CVE-2026-77141 published to NVD
2026-08-27 - Last updated in NVD database

Technical Details for CVE-2026-77141

Vulnerability Analysis

The vulnerability is a broken access control flaw in the frontend controller of the affected TYPO3 extension. The controller accepts a record identifier through a request argument and loads the corresponding club record from the database. It then executes the requested edit, update, or activate action against that record without verifying that the requester owns it.

An attacker enumerates or guesses a valid record UID and issues an HTTP request to the vulnerable action. The update action allows arbitrary field overwrites on records belonging to other users. The activate action allows an attacker to publish records that are still pending moderator approval, bypassing the review workflow entirely.

The flaw does not require authentication, credentials, or user interaction. The attack surface is any TYPO3 site running the vulnerable extension with the frontend plugin exposed.

Root Cause

The root cause is a missing authorization check between record resolution and action execution. The controller trusts the client-supplied UID and does not compare the record's owner (typically a fe_user reference) against the current frontend session. This is a canonical [CWE-639] Insecure Direct Object Reference pattern where the object key alone determines access.

Attack Vector

The attack is delivered over the network against the TYPO3 frontend. An attacker crafts a POST or GET request to the extension's plugin endpoint, sets the record UID argument to the target record, and supplies the payload fields for update or the trigger parameter for activate. The server processes the request without an ownership check and commits the change. See the TYPO3 Security Advisory #2026-019 for the vendor's technical description and fixed versions.

No verified proof-of-concept code has been published for this CVE. Refer to the vendor advisory for parameter names and controller action mappings.

Detection Methods for CVE-2026-77141

Indicators of Compromise

Unexpected modifications to club records with no corresponding authenticated session in TYPO3 logs
Records transitioning from a pending or hidden state to active without moderator action
HTTP requests to the extension's plugin endpoint containing edit, update, or activate action parameters from unauthenticated sources
Sequential or scripted access patterns against incrementing record UID values

Detection Strategies

Correlate TYPO3 sys_log and extension-specific change logs with web server access logs to flag record writes lacking an authenticated fe_user context
Alert on frontend POST requests to the vulnerable extension's action URIs where the session cookie is absent or unauthenticated
Baseline normal record state transitions and flag activations that skip the standard moderation workflow

Monitoring Recommendations

Enable verbose logging on the affected extension's controller actions and forward events to a central SIEM
Monitor database audit trails for UPDATE statements against the club records table originating from frontend traffic
Track anomalous rates of requests carrying the uid argument to the vulnerable plugin endpoint

How to Mitigate CVE-2026-77141

Immediate Actions Required

Apply the fixed extension version referenced in TYPO3 Security Advisory #2026-019 as soon as it is available in the TYPO3 Extension Repository (TER)
Audit club records for unauthorized modifications or unexpected activations since the extension was deployed
Restrict frontend access to the vulnerable plugin at the web server or WAF layer until the patch is applied

Patch Information

Consult TYPO3 Security Advisory #2026-019 for the fixed version numbers and upgrade instructions. The patch introduces ownership validation in the edit, update, and activate actions so that the current frontend user must own the resolved record before the action proceeds.

Workarounds

Disable the vulnerable extension's frontend plugin on affected pages until the patched version is installed
Block the plugin's action URIs with WAF rules that reject unauthenticated requests carrying edit, update, or activate parameters
Temporarily require frontend authentication on pages hosting the plugin through TYPO3 access restrictions

bash

# Example WAF rule concept (adapt to your engine)
# Deny unauthenticated frontend requests to the vulnerable actions
SecRule REQUEST_URI "@rx (?i)tx_[^=]+\[action\]=(update|activate|edit)" \
    "id:2026077141,phase:2,deny,status:403,\
     chain,msg:'CVE-2026-77141 - block unauthenticated action'"
  SecRule &REQUEST_COOKIES:fe_typo_user "@eq 0"