CVE-2026-49091: Kibana Log Injection Vulnerability – Impact & Remediation

Technical summary

CVE-2026-49091 is an improper output neutralization vulnerability (CWE-116) in Kibana that permits log injection attacks. An authenticated attacker can supply input containing terminal control sequences that are written unsanitized to log files. When a user views these logs in a terminal application that interprets ANSI escape codes or similar control sequences, the injected payloads execute, potentially rewriting displayed content, suppressing output, or inserting forged log entries. This attack vector aligns with CAPEC-93 (Log Injection-Tampering-Forging) and represents a post-authentication integrity compromise affecting log trustworthiness.

Business impact

Compromised log integrity directly threatens compliance, forensics, and incident response capabilities. An attacker with valid credentials could alter the appearance of audit logs, hide their own actions, or inject false evidence of legitimate activity—undermining non-repudiation and making root-cause analysis unreliable. In regulated environments (PCI-DSS, HIPAA, SOC 2), log tampering can create audit failures and regulatory violations. The HIGH severity score reflects the potential for widespread visibility and integrity harm across log-dependent security controls.

Affected systems

The vulnerability affects Elastic Kibana. Organizations running Kibana instances should verify their deployment versions against Elastic's advisory to confirm exposure scope. The attack requires authentication, so exposure is limited to users with valid access to ingest or manipulate logs.

Exploitability

Exploitation requires an authenticated user (PR:L) and involves user interaction—the victim must view the injected logs in a terminal that interprets control sequences (UI:R). The attack complexity is rated as High (AC:H), suggesting specific terminal types or configurations may be required for the control sequences to render. While not trivial, the barrier is practical; any user with legitimate log-writing privileges could potentially execute this attack. Public exploitation is not currently documented in KEV.

Remediation

Apply patches from Elastic as soon as they become available. Until patching is complete, implement output encoding or sanitization controls that strip or escape terminal control characters from logs before display. Review access controls to limit who can write to or influence log content. Monitor log files for suspicious sequences or anomalies in formatting. If logs are viewed primarily through Kibana's UI rather than raw terminal output, risk is reduced but should still be addressed.

Patch guidance

Monitor Elastic's security advisories for CVE-2026-49091 patch releases for Kibana. Apply patches to all affected instances in your environment. Before deploying patches to production, validate in a staging environment that the fix resolves the injection without breaking log parsing or existing integrations. Coordinate patching with your incident response and audit teams to avoid disruption during log reviews.

Detection guidance

Search logs for unusual terminal escape sequences (e.g., \033[, \x1b[) or other control characters that may indicate injection attempts. Monitor for changes in log appearance or formatting anomalies when viewing logs in terminals. Implement SIEM rules to alert on suspicious character sequences in log sources. Audit access patterns for users writing or manipulating logs outside normal workflows. Review terminal configurations used for log analysis to confirm they do not execute control sequences automatically.

Why prioritize this

This is a HIGH-severity post-authentication integrity attack affecting core security infrastructure (logs). While it requires valid credentials and user interaction, the damage potential—log tampering and audit trail corruption—is severe in regulated and security-sensitive environments. Prioritize patching for instances exposed to untrusted users or in high-compliance-requirement settings.

Risk score, explained

CVSS 3.1 score of 8.0 reflects HIGH severity: network-accessible (AV:N), high complexity (AC:H), low privileges required (PR:L), user interaction needed (UI:R), changed scope (S:C), and high impact across confidentiality, integrity, and availability (C:H/I:H/A:H). The high impact trio reflects the potential for widespread log falsification affecting security posture visibility and compliance.

Frequently asked questions