CVE-2025-37727 Overview
CVE-2025-37727 is an information disclosure vulnerability in Elastic Elasticsearch. The flaw stems from the insertion of sensitive information into log files [CWE-532] when auditing requests directed at the reindex API. Under specific preconditions, audit log entries can capture sensitive data associated with reindex operations, leading to a loss of confidentiality. An authenticated attacker with adjacent network access and low privileges can access this exposed data. Elastic disclosed the issue in security advisory ESA-2025-18 and released fixes in Elasticsearch versions 8.18.8, 8.19.5, 9.0.8, and 9.1.5.
Critical Impact
Sensitive information handled by the Elasticsearch reindex API can be persisted in audit logs, exposing confidential data to any actor with read access to those logs.
Affected Products
- Elastic Elasticsearch versions prior to 8.18.8
- Elastic Elasticsearch 8.19.x prior to 8.19.5
- Elastic Elasticsearch 9.0.x prior to 9.0.8 and 9.1.x prior to 9.1.5
Discovery Timeline
- 2025-10-10 - CVE-2025-37727 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-37727
Vulnerability Analysis
The vulnerability resides in how Elasticsearch's security audit subsystem records requests submitted to the reindex API. When audit logging is enabled, the server writes structured entries describing incoming API calls. For reindex requests, these entries can include sensitive fields that should not be persisted in plaintext audit records.
The issue is classified under CWE-532: Insertion of Sensitive Information into Log File. Exploitation requires an attacker positioned on an adjacent network with authenticated, low-privileged access to the cluster. The confidentiality impact is high, while integrity and availability are not affected. See the Elastic Discuss Security Update ESA-2025-18 for vendor details.
Root Cause
The root cause is inadequate scrubbing of request payloads before they are serialized into audit log entries. The reindex API accepts source and destination configuration, which may contain remote cluster credentials, query bodies, or other confidential parameters. The audit path did not sanitize these fields before writing them to disk.
Attack Vector
An authenticated user with access to submit reindex requests can trigger the logging behavior during normal operation. Any principal or process with subsequent read access to the audit log files, including operators, log-shippers, or downstream SIEM ingestion pipelines, can retrieve the exposed information. The attack vector is adjacent-network rather than fully remote, meaning the attacker must be on the same logical network segment as the Elasticsearch node.
No public proof-of-concept exploit has been published, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.
Detection Methods for CVE-2025-37727
Indicators of Compromise
- Audit log entries containing reindex API request bodies with populated source, remote, or query fields written in cleartext.
- Unexpected read access, copy operations, or exfiltration attempts targeting the Elasticsearch audit log directory.
- Presence of downstream copies of audit logs in SIEM or log-archival stores that contain reindex request bodies.
Detection Strategies
- Inspect existing Elasticsearch audit logs for reindex request events and identify entries containing credentials, tokens, or sensitive query terms.
- Correlate access to the audit log path with user identity to detect unauthorized reads by non-administrative accounts.
- Verify running Elasticsearch versions against the fixed releases 8.18.8, 8.19.5, 9.0.8, and 9.1.5.
Monitoring Recommendations
- Enable file integrity monitoring on the Elasticsearch audit log directory and alert on read access from unexpected principals.
- Forward Elasticsearch audit events into a centralized SIEM with strict role-based access control to limit exposure.
- Review log-retention policies and purge historical audit logs generated by vulnerable versions after confirming they are no longer required.
How to Mitigate CVE-2025-37727
Immediate Actions Required
- Upgrade Elasticsearch to 8.18.8, 8.19.5, 9.0.8, 9.1.5, or later, according to the deployed branch.
- Restrict filesystem and network access to audit log files so only trusted administrators can read them.
- Rotate any credentials or secrets that may have been captured in historical audit logs produced by vulnerable versions.
Patch Information
Elastic released fixed builds in security update ESA-2025-18. The corrected versions are Elasticsearch 8.18.8, 8.19.5, 9.0.8, and 9.1.5. Refer to the Elastic Discuss Security Update ESA-2025-18 advisory for full remediation guidance and download links.
Workarounds
- Disable audit logging for the reindex API endpoint if patching cannot be completed immediately, accepting the loss of audit coverage as a temporary trade-off.
- Tighten permissions on the audit log directory to restrict access to a minimal set of administrators.
- Sanitize or filter reindex-related audit entries in the log-shipping pipeline before they reach shared storage or SIEM indexes.
# Configuration example: restrict audit log directory permissions on Linux
chown -R elasticsearch:elasticsearch /var/log/elasticsearch
chmod 750 /var/log/elasticsearch
chmod 640 /var/log/elasticsearch/*_audit.json
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
