CVE-2026-63140 in Elasticsearch
Summary
by MITRE • 07/22/2026
Reachable Assertion (CWE-617) in Elasticsearch can lead to denial of service via Input Data Manipulation (CAPEC-153). A specially crafted search request containing a null value in a specific query clause causes an internal assertion to be raised during query parsing. Because Elasticsearch treats assertion failures as fatal errors, this terminates the affected node process. A low-privileged authenticated user with read access to at least one index can exploit this condition with a single request to cause a node to terminate, disrupting search availability. In a single-node deployment this fully stops Elasticsearch; in a multi-node cluster it reduces cluster capacity for each affected node.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 07/22/2026
Reachable assertion vulnerabilities represent a critical class of software flaws that can be triggered through input manipulation, as demonstrated by the CVE-2023-28215 vulnerability in Elasticsearch. This specific weakness falls under CWE-617 which defines reachable assertions as conditions where an assertion can be reached through normal program execution paths, typically due to improper input validation or handling of edge cases. The vulnerability manifests when Elasticsearch processes search requests containing null values within specific query clauses that trigger internal assertion failures during the parsing phase of query execution.
The technical implementation of this flaw exploits the fundamental architecture of Elasticsearch's query processing pipeline where malformed input data can cause the system to encounter assertions that are designed for debugging purposes but are not properly handled in production environments. When a specially crafted search request with null values enters the query parser, it causes an assertion failure that is treated as a fatal error rather than being gracefully managed or rejected. This design decision transforms what should be a controlled input validation error into a system termination event that completely halts Elasticsearch node operations.
The operational impact of this vulnerability extends beyond simple service disruption to create cascading effects in distributed environments where Elasticsearch clusters depend on multiple nodes for availability and performance. In single-node deployments, the assertion failure results in complete system outages requiring manual intervention and restart procedures that can take considerable time depending on cluster size and data volume. For multi-node clusters, the vulnerability creates capacity reduction scenarios where affected nodes become unavailable, forcing the cluster to redistribute workloads and potentially leading to degraded performance or even node failures if the system cannot maintain quorum requirements.
Authentication requirements for exploitation are relatively minimal, requiring only low-privileged authenticated access to at least one index within the Elasticsearch cluster. This access level allows attackers to craft malicious search requests that specifically target the assertion failure condition without needing administrative privileges or complex attack chains. The simplicity of the attack vector combined with the severe impact makes this vulnerability particularly dangerous in production environments where Elasticsearch serves as a critical data access layer for applications and services.
Mitigation strategies should focus on input validation enhancements and system resilience improvements to prevent assertion failures from terminating node processes. Organizations should implement comprehensive query parsing validation that explicitly handles null values and edge cases before they can trigger internal assertions. The recommended approach includes upgrading to patched versions of Elasticsearch where the vulnerability has been addressed through proper error handling mechanisms, implementing additional input sanitization layers, and configuring system-level protections that prevent assertion failures from causing process termination. Network segmentation and access controls should also be reviewed to limit exposure of Elasticsearch clusters to untrusted users or applications that might attempt exploitation.
This vulnerability aligns with several ATT&CK techniques including T1210 for exploitation of remote services and T1499 for denial of service attacks, demonstrating how seemingly minor software flaws can create significant operational impacts. The attack pattern follows CAPEC-153 methodology where input data manipulation leads to assertion failures that ultimately cause system termination. Organizations should also consider implementing monitoring solutions that can detect unusual process termination patterns or assertion failure events as early warning indicators for similar vulnerabilities in their Elasticsearch deployments and other software systems.