CVE-2026-72638 in Elasticsearch
Summary
by MITRE • 08/13/2026
Uncontrolled Recursion (CWE-674) in Elasticsearch can lead to denial of service via Input Data Manipulation (CAPEC-153). An authenticated user holding only low-privileged index creation permissions can submit a single request containing a specially crafted, malformed custom analysis definition that is resolved recursively without a cycle or depth check, exhausting the thread stack and terminating the affected node.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 08/13/2026
Uncontrolled recursion represents a fundamental vulnerability pattern that manifests when a program fails to properly terminate recursive function calls, leading to excessive resource consumption and system instability. This particular instance occurs within the elasticsearch ecosystem where the analysis framework processes custom analyzers without implementing proper depth or cycle detection mechanisms. The vulnerability specifically targets the recursive resolution of custom analysis definitions, which are components used to define how text should be processed and analyzed within the search platform. When an attacker crafts a malicious analyzer definition that references itself or creates circular dependencies, the system's recursive processing engine continues indefinitely until it exhausts available stack memory.
The technical exploitation of this vulnerability requires an authenticated user with minimal privileges, specifically the ability to create indices within elasticsearch. This low-privilege requirement significantly broadens the attack surface as it does not necessitate administrative access or elevated permissions. The attacker can construct a single request containing malformed analysis definitions that appear legitimate but contain recursive references. The system processes these definitions through its internal analyzer resolution mechanism without any safeguards against infinite recursion, ultimately causing thread stack exhaustion and complete node termination. This behavior aligns with the capec-153 category of input data manipulation where attackers manipulate input parameters to cause unintended program execution patterns rather than directly exploiting code vulnerabilities.
The operational impact of this vulnerability extends beyond simple denial of service as it can effectively take entire elasticsearch clusters offline, disrupting search functionality and potentially affecting applications that depend on real-time data retrieval. The recursive nature means that even a single malicious request can bring down the affected node, making this particularly dangerous in production environments where cluster stability is paramount. From a security perspective, this vulnerability demonstrates the importance of implementing proper input validation and recursion depth checks in complex processing frameworks. The attack vector leverages legitimate system functionality to create an abnormal execution state, making it difficult to detect through traditional network monitoring approaches.
Mitigation strategies for this vulnerability should focus on implementing comprehensive recursion detection mechanisms within the analysis framework. Organizations should deploy proper depth limiting configurations that prevent recursive resolution beyond predetermined limits, typically measured in analyzer nesting levels or maximum stack depth. The implementation should follow established security practices such as those outlined in the owasp top ten and nist cybersecurity framework guidelines for preventing denial of service attacks. Additionally, implementing proper input sanitization and validation controls can help detect malformed analyzer definitions before they are processed. System administrators should also consider implementing resource monitoring and alerting mechanisms that can detect unusual memory consumption patterns or thread exhaustion events. From an att&ck perspective, this vulnerability maps to the privilege escalation and denial of service techniques where attackers leverage legitimate system capabilities to cause unintended behavior, making it important for security teams to monitor for anomalous usage patterns in index creation operations.
The broader implications of this vulnerability highlight the need for robust defensive programming practices in enterprise search platforms and other systems that process user-defined configurations. It demonstrates how seemingly benign features like customizable analyzers can become attack vectors when proper safeguards are not implemented. Organizations should conduct regular security assessments focusing on recursive processing patterns within their systems, particularly in areas where user input is processed through complex transformation engines. The vulnerability also emphasizes the importance of principle of least privilege implementation, as even low-privilege users with index creation capabilities can cause significant damage to system availability. Regular updates and patch management become critical in addressing such vulnerabilities that exist in widely deployed enterprise software platforms like elasticsearch.