CVE-2023-5256: Drupal Privilege Escalation Vulnerability

CVE-2023-5256 Overview

CVE-2023-5256 is an information disclosure vulnerability affecting Drupal's JSON:API module that can lead to privilege escalation. In certain scenarios, the JSON:API module outputs error backtraces that may expose sensitive information. When specific caching configurations are in place, this sensitive data can be cached and subsequently made available to anonymous users, potentially enabling unauthorized privilege escalation.

Critical Impact
Sensitive information cached and exposed to anonymous users can lead to privilege escalation, compromising site confidentiality and integrity.

Affected Products

Drupal Core with JSON:API module enabled
Drupal versions with vulnerable JSON:API implementations
Sites utilizing caching configurations that store error responses

Discovery Timeline

2023-09-28 - CVE-2023-5256 published to NVD
2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-5256

Vulnerability Analysis

This vulnerability stems from improper handling of error responses in Drupal's JSON:API module. When certain error conditions occur, the module generates detailed backtraces that may contain sensitive configuration data, internal paths, database credentials, or other security-critical information. The vulnerability is classified under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor).

The attack requires network access and some level of authenticated access to trigger the error conditions. However, the critical aspect is that once sensitive information is leaked into error responses, caching mechanisms may store this data and serve it to unauthenticated users, effectively escalating their privileges by exposing information they should not have access to.

Importantly, only sites with the JSON:API module enabled are affected. The core REST module and contributed GraphQL modules are not impacted by this vulnerability.

Root Cause

The root cause lies in the JSON:API module's error handling implementation, which fails to properly sanitize or suppress detailed backtrace information in error responses under certain conditions. When combined with caching layers that do not differentiate between authenticated and unauthenticated request contexts for error responses, sensitive data becomes persistently exposed.

Attack Vector

The attack vector is network-based, requiring an attacker to trigger specific error conditions in the JSON:API module. The exploitation scenario involves:

An attacker with low-level privileges sends crafted requests to JSON:API endpoints designed to trigger error conditions
The JSON:API module returns detailed backtrace information in error responses
Caching mechanisms store these error responses without proper access control segregation
Anonymous users subsequently access cached error responses containing sensitive information
Exposed information can be leveraged for further attacks or privilege escalation

The vulnerability mechanism involves improper error handling in the JSON:API module's response generation. When errors occur during API request processing, the module may include stack traces and internal application state in the response body. For detailed technical information, refer to the Drupal Security Advisory SA-CORE-2023-006.

Detection Methods for CVE-2023-5256

Indicators of Compromise

Unexpected backtrace data appearing in JSON:API response logs
Cached responses containing internal path information or configuration details
Anomalous access patterns to JSON:API endpoints from anonymous users
Error responses in cache storage that contain sensitive application data

Detection Strategies

Monitor JSON:API endpoint responses for unexpected backtrace or debug information
Audit cache contents for sensitive information exposure
Review web server logs for unusual error response patterns on API endpoints
Implement content inspection rules to detect backtrace patterns in outbound API responses

Monitoring Recommendations

Enable detailed logging for JSON:API module activity
Configure cache monitoring to alert on storage of error responses
Set up intrusion detection signatures for error backtrace patterns in HTTP responses
Monitor for privilege escalation indicators following API error events

How to Mitigate CVE-2023-5256

Immediate Actions Required

Apply the latest Drupal security update as referenced in SA-CORE-2023-006
If immediate patching is not possible, disable the JSON:API module
Clear all caches after applying patches or mitigations
Review cached content for any previously exposed sensitive information

Patch Information

Drupal has released security patches to address this vulnerability. Administrators should update to the latest patched version of Drupal Core as detailed in the Drupal Security Advisory SA-CORE-2023-006. After applying the update, ensure all site caches are cleared to remove any potentially compromised cached data.

Workarounds

Uninstall or disable the JSON:API module if it is not required for site functionality
Configure caching layers to exclude error responses from being cached
Implement response filtering to strip backtrace information from API outputs
Restrict access to JSON:API endpoints using web server or firewall rules

bash

# Disable JSON:API module via Drush (temporary workaround)
drush pm:uninstall jsonapi

# Clear all Drupal caches after applying mitigation
drush cache:rebuild