CVE-2023-45725: Apache CouchDB Information Disclosure Flaw

CVE-2023-45725 Overview

CVE-2023-45725 is an information disclosure vulnerability in Apache CouchDB that allows design document functions to expose sensitive authorization or session cookie headers of users accessing the documents. This vulnerability affects specific design document functions that receive user HTTP request objects, potentially enabling attackers to steal user credentials and hijack sessions.

Critical Impact

Attackers who can insert malicious design documents into a CouchDB database may be able to steal session cookies and authorization headers from users accessing those documents, leading to account takeover and unauthorized access.

Affected Products

• Apache CouchDB (all versions prior to patched releases)

Discovery Timeline

• 2023-12-13 - CVE-2023-45725 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-45725

Vulnerability Analysis

This vulnerability exists in Apache CouchDB's design document functionality, specifically affecting functions that process HTTP request objects from users. The affected design document functions are list, show, rewrite, and update. When a user accesses a document through one of these functions, the function receives the user's HTTP request object, which includes sensitive headers such as authorization tokens and session cookies.

A malicious actor who has the ability to insert design documents into a CouchDB database can craft documents that exploit this behavior. The attack requires two conditions: first, the attacker must have write access to insert design documents into the database, and second, the attacker must trick a legitimate user into accessing a function from that malicious design document.

Root Cause

The root cause of this vulnerability is improper information exposure (CWE-200) in the design document function handling. The design document functions (list, show, rewrite, and update) receive the full HTTP request object including sensitive headers without adequate sanitization or restriction. This architectural decision allows design documents to access headers that should remain confidential, creating a pathway for credential theft.

Attack Vector

The attack can be executed through multiple techniques once a malicious design document is in place:

1. HTML-based Exfiltration: The attacker crafts HTML-like output that leaks the session component through the response.

2. External Resource Injection: The session cookie is embedded as part of an external resource request, such as an image URL parameter, causing the user's browser to send the credential to an attacker-controlled server.

3. Local Document Storage: Using the update function, the attacker stores the stolen credential directly in a _local document within the database for later retrieval.

The attack requires user interaction, as the victim must navigate to or be redirected to a URL that triggers the malicious design document function.

Detection Methods for CVE-2023-45725

Indicators of Compromise

• Unexpected design documents appearing in CouchDB databases, particularly those with list, show, rewrite, or update functions
• Design document functions that reference req.headers or specifically access cookie or authorization header fields
• Unusual external resource references in design document outputs pointing to external domains
• New or modified _local documents containing encoded strings that may be exfiltrated credentials

Detection Strategies

• Audit all design documents in CouchDB databases for functions that access HTTP request headers
• Monitor for creation or modification of design documents, especially from untrusted or low-privilege users
• Review web server logs for unusual patterns of access to design document endpoints followed by external requests
• Implement content security policies to detect and block unauthorized external resource loading

Monitoring Recommendations

• Enable comprehensive logging for design document access and modifications in CouchDB
• Set up alerts for design document changes in production databases
• Monitor outbound network connections from CouchDB servers for unexpected external communications
• Regularly audit user permissions to ensure only trusted users can create or modify design documents

How to Mitigate CVE-2023-45725

Immediate Actions Required

• Review and audit all existing design documents in your CouchDB instances for suspicious header access patterns
• Restrict design document creation and modification to trusted administrators only
• Avoid using design documents from untrusted sources that may attempt to access or manipulate request object headers
• Consider temporarily disabling unused design document functions (list, show, rewrite, update) if they are not required

Patch Information

Apache has released security updates addressing this vulnerability. Administrators should review the official CouchDB CVE-2023-45725 Documentation and the Apache Mailing List Discussion for specific version information and update instructions. Apply the latest security patches to all CouchDB instances as soon as possible.

Workarounds

• Implement strict access controls to prevent untrusted users from creating or modifying design documents
• Avoid using design documents from untrusted sources that may attempt to access or manipulate request object headers
• Configure network segmentation to limit CouchDB's ability to make outbound connections
• Enable and enforce Content Security Policy headers to prevent external resource loading from CouchDB responses

# Configuration example - Restrict design document modification
# In CouchDB local.ini, configure admin-only design document access
[couchdb]
; Ensure only admins can modify design documents
admin_only_all_dbs = true

[chttpd]
; Limit allowed methods for non-admin users if applicable
; Review authentication requirements for _design document endpoints
require_valid_user = true