CVE-2026-49088: Kibana Information Disclosure Vulnerability

CVE-2026-49088 Overview

CVE-2026-49088 is an information disclosure vulnerability in Kibana caused by the insertion of sensitive information into log files [CWE-532]. When the optional application performance monitoring (APM) instrumentation is enabled, Kibana records sensitive request header values in application logs. Operators with log access can then read those values, including credentials or session material contained in headers.

Elastic published the fix in advisory ESA-2026-50 covering Kibana versions 8.18.9, 8.19.6, 9.0.8, and 9.1.6. The issue requires high privileges and network access to trigger, and it affects confidentiality only. No exploit code is publicly available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

Critical Impact
Request headers written to Kibana logs can expose authentication tokens, API keys, and session identifiers to any operator with log-read privileges.

Affected Products

Kibana versions prior to 8.18.9 on the 8.18 branch
Kibana versions prior to 8.19.6 and 9.0.8 on the 8.19 and 9.0 branches
Kibana versions prior to 9.1.6 on the 9.1 branch with APM instrumentation enabled

Discovery Timeline

2026-07-01 - CVE-2026-49088 published to the National Vulnerability Database
2026-07-01 - Last updated in NVD database

Technical Details for CVE-2026-49088

Vulnerability Analysis

Kibana ships with optional APM instrumentation that traces incoming HTTP requests for performance analysis. When operators enable this feature, the instrumentation captures request metadata and writes it to application logs. The captured metadata includes header values that carry authentication and session data.

The vulnerability requires an attacker to already hold high privileges within the environment. Attack complexity is high because the attacker must reach log storage and correlate captured headers with active sessions. The issue impacts confidentiality only; integrity and availability are not affected.

Elastic categorizes this weakness under [CWE-532], Insertion of Sensitive Information into Log File. The advisory ESA-2026-50 lists patched versions 8.18.9, 8.19.6, 9.0.8, and 9.1.6.

Root Cause

The APM instrumentation code path does not filter sensitive HTTP header names before serializing request context to log output. Headers such as Authorization, Cookie, and custom API key headers pass through unredacted. Logs written to disk or forwarded to centralized logging pipelines retain those values.

Attack Vector

An operator or attacker with log-read access harvests recorded headers from Kibana log files or downstream log stores. The attacker then replays captured session cookies or bearer tokens against Kibana or associated Elastic services. Because the vector is network-adjacent post-exposure, the CVSS metric marks it as a network attack path despite requiring internal log access.

No public proof-of-concept exists. Refer to the Elastic Security Update ESA-2026-50 for vendor technical details.

Detection Methods for CVE-2026-49088

Indicators of Compromise

Kibana log entries containing Authorization, Cookie, x-api-key, or elastic-api-version header values in plaintext
APM transaction records that include full HTTP header dictionaries for Kibana request spans
Unexpected access to Kibana log directories or centralized log indices by non-administrative accounts

Detection Strategies

Grep Kibana log files for regular expressions matching bearer tokens, basic auth strings, and session cookie patterns
Audit APM index documents in Elasticsearch for http.request.headers fields containing credential-bearing keys
Correlate log-access events with subsequent authentication attempts reusing captured tokens

Monitoring Recommendations

Enable file integrity and access monitoring on the Kibana log directory and any forwarded log aggregators
Alert on read operations against APM indices by identities outside the observability team
Track configuration changes that enable APM instrumentation on Kibana nodes

How to Mitigate CVE-2026-49088

Immediate Actions Required

Upgrade Kibana to 8.18.9, 8.19.6, 9.0.8, or 9.1.6 as appropriate for the deployed branch
Rotate any credentials, API keys, and session tokens that may have transited Kibana while APM instrumentation was active
Restrict log access to a minimal set of administrators and review historical log-read activity

Patch Information

Elastic released fixed versions 8.18.9, 8.19.6, 9.0.8, and 9.1.6. Details and download links are published in the Elastic Security Update ESA-2026-50. Apply the patch on all Kibana nodes before re-enabling APM instrumentation.

Workarounds

Disable Kibana APM instrumentation until upgrades are complete
Purge existing Kibana application logs and APM transaction documents that captured sensitive headers
Configure log processors to redact Authorization, Cookie, and API key headers before storage or forwarding

bash

# Configuration example: disable APM instrumentation in kibana.yml
elastic.apm.active: false
elastic.apm.captureHeaders: false