CVE-2024-37280: Elastic Elasticsearch DOS Vulnerability

CVE-2024-37280 Overview

A denial of service vulnerability was discovered in Elasticsearch affecting document ingestion when an index template contains a dynamic field mapping of "passthrough" type. Under certain circumstances, ingesting documents in this index causes a StackOverflow exception to be thrown, ultimately leading to a Denial of Service condition. It is important to note that passthrough fields is an experimental feature in Elasticsearch.

Critical Impact

Attackers with high privileges can trigger a StackOverflow exception during document ingestion, causing Elasticsearch nodes to become unresponsive and disrupting search and analytics operations.

Affected Products

• Elastic Elasticsearch (versions prior to 8.14.0)

Discovery Timeline

• 2024-06-13 - CVE-2024-37280 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-37280

Vulnerability Analysis

This vulnerability is classified under CWE-122 (Heap-based Buffer Overflow) and CWE-787 (Out-of-bounds Write), though the primary manifestation is a stack overflow condition. The flaw exists in Elasticsearch's document ingestion pipeline when processing index templates that utilize the experimental "passthrough" dynamic field mapping type.

When documents are ingested into an index configured with passthrough field mappings, specific document structures can trigger recursive processing that exhausts the available stack space. This results in a StackOverflowException being thrown, which crashes the ingestion process and can render Elasticsearch nodes unresponsive.

The attack requires network access and high privileges (administrative access to create or modify index templates), which limits the attack surface. However, in multi-tenant environments or systems where template management is delegated, this vulnerability poses a significant availability risk.

Root Cause

The root cause lies in improper handling of recursive field mappings within the passthrough type implementation. When certain nested document structures are processed against a passthrough-type dynamic field mapping, the recursion depth exceeds the JVM's stack capacity, leading to a stack overflow condition. This is an implementation flaw in an experimental feature that did not properly bound recursion depth or implement iterative processing for deeply nested structures.

Attack Vector

The attack vector is network-based and requires high privileges. An attacker must have sufficient permissions to either create index templates with passthrough field mappings or ingest documents into an existing index with such mappings. The attack scenario involves:

1. Creating or identifying an index template with a "passthrough" type dynamic field mapping
2. Crafting a document with a structure that triggers deep recursion during field processing
3. Ingesting the malicious document to trigger the StackOverflow exception
4. Repeating the attack to sustain denial of service conditions

The vulnerability exploits the experimental passthrough field mapping feature. When a document containing deeply nested or self-referential structures is ingested, the field mapping processor enters an unbounded recursive loop, ultimately exhausting the JVM stack and crashing the ingestion thread. For detailed technical information, see the Elastic Security Update Discussion.

Detection Methods for CVE-2024-37280

Indicators of Compromise

• Elasticsearch nodes experiencing unexpected StackOverflowException errors in logs
• Repeated crashes or restarts of Elasticsearch ingestion processes
• Index templates containing "passthrough" type dynamic field mappings combined with unusual document ingestion patterns
• JVM crash dumps indicating stack exhaustion during document processing

Detection Strategies

• Monitor Elasticsearch logs for StackOverflowException entries, particularly those occurring during document ingestion operations
• Audit index templates for the use of experimental "passthrough" type field mappings
• Implement alerting on Elasticsearch node availability and ingestion pipeline health metrics
• Review recent template changes for introduction of passthrough field mappings

Monitoring Recommendations

• Enable verbose logging for Elasticsearch ingestion pipelines to capture early warning signs
• Configure JVM monitoring to track stack usage and thread health
• Set up cluster health monitoring with alerts for node unavailability
• Implement rate limiting and anomaly detection on document ingestion endpoints

How to Mitigate CVE-2024-37280

Immediate Actions Required

• Upgrade Elasticsearch to version 8.14.0 or later where this vulnerability is patched
• Audit existing index templates and remove or disable passthrough type field mappings until patching is complete
• Restrict permissions for index template creation and modification to trusted administrators only
• Monitor ingestion pipelines for signs of exploitation attempts

Patch Information

Elastic has released a security update addressing this vulnerability in Elasticsearch version 8.14.0. Organizations should prioritize upgrading to this version or later. The security advisory is available at the Elastic Security Update Discussion. Additional vendor information is available from the NetApp Security Advisory.

Workarounds

• Avoid using the experimental "passthrough" type dynamic field mapping until the cluster is patched
• Implement input validation on documents before ingestion to detect potentially malicious nested structures
• Restrict index template management permissions using Elasticsearch's role-based access control
• Consider deploying Elasticsearch behind a web application firewall with rules to detect anomalous document structures

# Configuration example
# Audit existing index templates for passthrough field mappings
curl -X GET "localhost:9200/_index_template?pretty" | grep -i passthrough

# Review and update role-based access control to restrict template management
# Example: Create a role that excludes template management permissions
curl -X PUT "localhost:9200/_security/role/restricted_user" -H 'Content-Type: application/json' -d'
{
  "cluster": ["monitor"],
  "indices": [
    {
      "names": ["*"],
      "privileges": ["read", "write"]
    }
  ]
}'