CVE-2023-46673: Elastic Elasticsearch DOS Vulnerability

CVE-2023-46673 Overview

CVE-2023-46673 is a Denial of Service vulnerability in Elastic Elasticsearch that allows attackers to crash an Elasticsearch node by submitting malformed scripts through the script processor of an Ingest Pipeline when calling the Simulate Pipeline API. This vulnerability affects the availability of Elasticsearch clusters and can be exploited remotely without authentication.

Critical Impact

Unauthenticated remote attackers can cause Elasticsearch nodes to crash, potentially disrupting data indexing, search capabilities, and overall cluster stability in production environments.

Affected Products

• Elastic Elasticsearch (versions prior to 7.17.14)
• Elastic Elasticsearch (versions 8.x prior to 8.10.3)

Discovery Timeline

• 2023-11-22 - CVE-2023-46673 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-46673

Vulnerability Analysis

This vulnerability stems from improper handling of exceptions (CWE-755) in Elasticsearch's Ingest Pipeline script processor. When the Simulate Pipeline API processes specially crafted malformed scripts, the application fails to properly handle the resulting error condition, leading to a node crash.

The Ingest Pipeline feature in Elasticsearch allows users to pre-process documents before indexing. The script processor within these pipelines enables custom transformations using Painless scripting language. When malformed scripts are submitted through the Simulate Pipeline API—which is designed to test pipeline configurations without actually indexing data—the improper exception handling causes the entire Elasticsearch node to terminate unexpectedly.

This is particularly concerning because the Simulate Pipeline API is often accessible to users with lower privilege levels since it's intended for testing purposes, and the attack can be executed over the network without user interaction.

Root Cause

The root cause is improper exception handling (CWE-755: Improper Handling of Exceptional Conditions) within the script processor component. When parsing and executing malformed Painless scripts, the processor encounters an unexpected exception state that is not gracefully caught and handled, causing the node process to crash rather than returning an appropriate error response to the caller.

Attack Vector

An attacker can exploit this vulnerability by sending specially crafted HTTP requests to the Elasticsearch Simulate Pipeline API endpoint (/_ingest/pipeline/_simulate or /_ingest/pipeline/{id}/_simulate). The request would contain a malformed script within the pipeline definition's script processor configuration. When Elasticsearch attempts to parse or validate this malformed script during simulation, the improper exception handling causes the node to crash.

The attack requires network access to the Elasticsearch API endpoint but does not require authentication if the cluster is misconfigured with open access, which is unfortunately common in development and improperly secured production environments.

Detection Methods for CVE-2023-46673

Indicators of Compromise

• Unexpected Elasticsearch node crashes or restarts without clear memory or resource exhaustion causes
• Unusual volume of requests to /_ingest/pipeline/_simulate endpoints
• Log entries showing unhandled exceptions in the script processor component immediately before node termination
• Repeated cluster state changes due to nodes dropping and rejoining

Detection Strategies

• Monitor Elasticsearch audit logs for requests to Simulate Pipeline API endpoints with unusual or malformed payload structures
• Implement network-level detection rules for HTTP requests containing suspicious script processor configurations targeting ingest pipeline endpoints
• Configure alerting on Elasticsearch node crashes that correlate with recent API activity on pipeline simulation endpoints
• Deploy SentinelOne Singularity to detect anomalous process termination patterns and potential exploitation attempts

Monitoring Recommendations

• Enable and centralize Elasticsearch slow logs and audit logs for correlation analysis
• Configure cluster health monitoring to alert immediately on node departure events
• Implement rate limiting on ingest pipeline simulation endpoints to slow potential exploitation attempts
• Monitor for reconnaissance activity such as enumeration of existing pipelines via /_ingest/pipeline GET requests

How to Mitigate CVE-2023-46673

Immediate Actions Required

• Upgrade Elasticsearch to version 7.17.14 or later for the 7.x branch
• Upgrade Elasticsearch to version 8.10.3 or later for the 8.x branch
• Restrict access to the Simulate Pipeline API to trusted users only using role-based access control
• Ensure Elasticsearch is not exposed directly to the internet without proper authentication and network segmentation

Patch Information

Elastic has released security patches addressing this vulnerability in Elasticsearch versions 7.17.14 and 8.10.3. Organizations should review the Elastic Security Update ESA-2023-24 for detailed upgrade instructions and additional security resources available at the Elastic Community Security Resources page.

Workarounds

• Implement network-level firewall rules to restrict access to the /_ingest/pipeline/_simulate endpoint to trusted IP addresses only
• Configure Elasticsearch security features to require authentication for all API endpoints, particularly ingest pipeline operations
• Deploy a reverse proxy in front of Elasticsearch to filter and validate requests before they reach the cluster
• Use Elasticsearch's built-in role-based access control to remove manage_ingest_pipelines privileges from non-essential users

# Example: Restrict access to ingest pipeline API using Elasticsearch role configuration
# Create a role that excludes dangerous ingest operations
PUT /_security/role/restricted_user
{
  "cluster": ["monitor"],
  "indices": [
    {
      "names": ["your-index-*"],
      "privileges": ["read", "write"]
    }
  ]
}
# Note: This role intentionally omits cluster privileges like
# "manage_ingest_pipelines" to prevent pipeline simulation access