CVE-2026-77127 Overview
CVE-2026-77127 is an information disclosure vulnerability affecting a TYPO3 extension that exposes an unrestricted backend AJAX endpoint used for inline editing. The endpoint fails to enforce field-level access controls, allowing an authenticated low-privileged backend user to specify arbitrary table, field, and record parameters. A crafted request triggers an error response that echoes the current database value of the requested field. Attackers can extract sensitive data, including backend and frontend user password hashes. Exploitation requires a valid TYPO3 backend account with access to the extension's backend module. The issue is tracked under [CWE-639] Authorization Bypass Through User-Controlled Key.
Critical Impact
Authenticated low-privileged backend users can extract arbitrary database field values, including password hashes for backend and frontend accounts, enabling downstream credential attacks.
Affected Products
- TYPO3 third-party extension referenced in TYPO3 Security Advisory 2026-016
- TYPO3 backend deployments exposing the affected extension module
- Environments granting low-privileged backend users access to the extension
Discovery Timeline
- 2026-08-25 - CVE-2026-77127 published to NVD
- 2026-08-26 - Last updated in NVD database
Technical Details for CVE-2026-77127
Vulnerability Analysis
The vulnerability resides in a backend AJAX endpoint that handles inline editing operations. The endpoint accepts client-supplied table, field, and record identifier parameters without validating whether the requesting user is authorized to read or modify the referenced field. When the supplied parameters trigger a server-side error, the resulting error message reflects the current database value of the targeted field back to the requester.
This behavior allows an authenticated attacker to enumerate arbitrary tables and fields within the TYPO3 database. Because TYPO3 stores password hashes in the be_users and fe_users tables, an attacker can request those fields and receive the hash values in error responses. Recovered hashes support offline cracking and lateral movement across the TYPO3 installation.
Root Cause
The root cause is missing authorization on a user-controlled key, classified as [CWE-639]. The endpoint trusts the table and field parameters supplied by the client and does not consult TYPO3's field-level access control layer before reading data. A secondary flaw is verbose error handling that reflects backend data values to authenticated but unauthorized users.
Attack Vector
Exploitation is network-based and requires an authenticated TYPO3 backend account with access to the vulnerable extension's module. The attacker sends a crafted AJAX request to the inline-edit endpoint, supplying be_users or fe_users as the table and password as the field. The endpoint returns an error containing the target row's password hash. Refer to the TYPO3 Security Advisory 2026-016 for endpoint specifics and fixed version information.
Detection Methods for CVE-2026-77127
Indicators of Compromise
- Backend AJAX requests from low-privileged accounts referencing be_users, fe_users, or other sensitive tables in table or field parameters
- Repeated error responses from the extension's inline editing endpoint containing hash-like strings
- Unusual enumeration patterns iterating through uid values against the inline edit endpoint
Detection Strategies
- Inspect TYPO3 web server access logs for POST requests to the extension's inline edit AJAX route with unexpected table or field parameters
- Correlate backend user session identifiers with anomalous volumes of inline edit calls to detect enumeration attempts
- Alert on outbound response bodies from the endpoint that contain bcrypt or Argon2 hash prefixes such as $2y$ or $argon2i$
Monitoring Recommendations
- Enable TYPO3 backend audit logging and forward events to a centralized logging platform for correlation
- Monitor authentication logs for password resets and successful logins that follow suspicious backend activity, indicating potential hash cracking
- Baseline normal inline editing behavior per user role and alert on deviations against sensitive tables
How to Mitigate CVE-2026-77127
Immediate Actions Required
- Apply the fixed extension version identified in TYPO3 Security Advisory 2026-016 without delay
- Audit backend user accounts and remove access to the affected extension's module for users who do not require it
- Rotate credentials for any backend or frontend accounts whose hashes may have been exposed while the vulnerability was reachable
Patch Information
Update the affected TYPO3 extension to the patched release listed in the vendor advisory. Consult the TYPO3 Security Advisory 2026-016 for the exact fixed version and upgrade instructions. Verify the installed version through the TYPO3 Extension Manager after patching.
Workarounds
- Restrict access to the vulnerable extension's backend module using TYPO3 backend user group permissions until patching is complete
- Temporarily disable the extension in installations where it is not actively required
- Enforce strong password policies and re-hash stored credentials after remediation to reduce the value of any previously disclosed hashes
# Example: restrict module access via TYPO3 CLI after installing the fix
vendor/bin/typo3 extension:list | grep <extension_key>
vendor/bin/typo3 extension:deactivate <extension_key>
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
