CVE-2023-26268: Apache CouchDB Information Disclosure

CVE-2023-26268 Overview

CVE-2023-26268 is an information disclosure vulnerability affecting Apache CouchDB and IBM Cloudant that allows design documents with matching document IDs, from databases on the same cluster, to share a mutable JavaScript environment. This occurs when using specific design document functions including validate_doc_update, list, filter, filter views (using view functions as filters), rewrite, and update. The vulnerability does not affect map/reduce or search (Dreyfus) index functions.

Critical Impact

Untrusted design documents may cache or store sensitive data in the shared JavaScript environment, potentially exposing information across database boundaries within the same cluster.

Affected Products

• Apache CouchDB (versions prior to 3.3.2)
• Apache CouchDB (versions prior to 3.2.3 in the 3.2.x branch)
• IBM Cloudant

Discovery Timeline

• 2023-05-02 - CVE CVE-2023-26268 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-26268

Vulnerability Analysis

This vulnerability stems from improper isolation of JavaScript execution environments within Apache CouchDB's design document processing system. When multiple databases on the same cluster contain design documents with identical document IDs, these documents may inadvertently share the same mutable JavaScript runtime context.

The shared environment creates a pathway for information leakage between databases that should otherwise be isolated. An attacker with the ability to create or modify design documents could potentially exploit this behavior to access or manipulate data from other databases on the same cluster. The vulnerability specifically affects several JavaScript-based design document functions that handle document validation, list generation, filtering, URL rewriting, and document updates.

Since the JavaScript environment is mutable, data cached or stored by one design document's execution could persist and be accessible to subsequent executions from a different database's design document sharing the same ID. This cross-database information exposure represents a significant confidentiality concern in multi-tenant CouchDB deployments.

Root Cause

The root cause lies in CouchDB's JavaScript environment isolation mechanism for design document execution. The database engine fails to properly segregate JavaScript contexts when design documents across different databases share identical document IDs, allowing mutable state to persist between executions.

Attack Vector

An attacker could exploit this vulnerability by creating a malicious design document with a document ID that matches an existing design document in a target database on the same cluster. The attacker's design document could then access data cached or stored in the shared JavaScript environment by the target's design document functions. This attack requires network access to the CouchDB instance and the ability to create design documents, though no authentication may be required depending on the server's configuration.

The affected functions (validate_doc_update, list, filter, filter views, rewrite, and update) are commonly used in CouchDB applications for document processing and validation workflows, making this attack vector potentially impactful in production environments.

Detection Methods for CVE-2023-26268

Indicators of Compromise

• Unusual design document creation activity, particularly documents with IDs matching existing design documents across databases
• Unexpected data access patterns or queries against databases from design document functions
• Design documents from untrusted sources appearing in production databases
• Anomalous JavaScript execution behavior in CouchDB logs

Detection Strategies

• Monitor CouchDB audit logs for design document creation and modification events across all databases
• Implement alerting for design documents with duplicate IDs across database boundaries
• Review design document sources and validate their origin before deployment
• Enable verbose logging for design document function execution to track cross-database interactions

Monitoring Recommendations

• Establish baseline metrics for design document activity and alert on deviations
• Regularly audit all design documents in the cluster for unexpected or unauthorized entries
• Monitor for attempts to access the CouchDB API endpoints used for design document management
• Configure network monitoring to detect unusual traffic patterns to CouchDB instances

How to Mitigate CVE-2023-26268

Immediate Actions Required

• Upgrade Apache CouchDB to version 3.3.2 or 3.2.3 immediately
• Audit existing design documents across all databases in the cluster for matching document IDs
• Remove or rename design documents from untrusted sources
• Restrict permissions for design document creation to trusted administrators only

Patch Information

Apache has released patched versions that address this vulnerability. Users should upgrade to Apache CouchDB 3.3.2 or 3.2.3 depending on their version branch. For detailed patch information and upgrade instructions, refer to the CouchDB CVE-2023-26268 Advisory.

IBM Cloudant users should consult IBM's security advisories for specific remediation guidance applicable to their deployment.

Workarounds

• Avoid using design documents from untrusted sources that may attempt to cache or store data in the JavaScript environment
• Implement strict access controls limiting who can create or modify design documents
• Audit and sanitize all existing design documents, ensuring unique document IDs across database boundaries
• Consider isolating sensitive databases to separate CouchDB clusters until patching is complete

# Check current CouchDB version
curl -s http://localhost:5984/ | grep version

# Verify design documents across databases for duplicate IDs
for db in $(curl -s http://localhost:5984/_all_dbs | jq -r '.[]'); do
  echo "Database: $db"
  curl -s "http://localhost:5984/$db/_all_docs?startkey=\"_design/\"&endkey=\"_design0\"" | jq '.rows[].id'
done