CVE-2026-49091: Kibana Log Injection Vulnerability

CVE-2026-49091 Overview

CVE-2026-49091 is a log injection vulnerability in Elastic Kibana caused by Improper Output Neutralization for Logs [CWE-117]. Attackers can supply specially crafted input that Kibana writes to log files without sanitizing control characters or terminal escape sequences. When an operator later views the affected logs in a terminal that interprets these sequences, the injected content can alter displayed log data, hide malicious activity, or mislead incident responders.

Critical Impact
Attackers with low-privileged access can forge log entries and manipulate terminal output, undermining audit integrity and incident investigation reliability.

Affected Products

Elastic Kibana (versions addressed in the ESA-2026-53 advisory)
Kibana 7.17.x branch (patched in 7.17.15)
Kibana 8.x branch (patched in 8.11.1)

Discovery Timeline

2026-07-01 - CVE-2026-49091 published to NVD
2026-07-02 - Last updated in NVD database

Technical Details for CVE-2026-49091

Vulnerability Analysis

The vulnerability resides in Kibana's logging subsystem, which writes user-controllable input to log files without neutralizing dangerous characters. An authenticated attacker can inject ANSI escape sequences, carriage returns, or newline characters into fields that are eventually logged. Because these sequences are preserved verbatim in log files, they execute when an administrator reviews the logs in a terminal emulator that interprets control codes.

The issue is tracked under [CWE-116] (Improper Encoding or Escaping of Output) and mapped to [CAPEC-93] (Log Injection-Tampering-Forging). The attack chain requires user interaction because impact only materializes when a human reviews the tainted log data. However, the scope changes from the vulnerable Kibana component to the operator's terminal session, expanding the blast radius.

Root Cause

Kibana does not apply output encoding to log records before writing them to disk. Control characters such as \\x1b (escape), \r (carriage return), and \n (newline) pass through unchanged. Terminal emulators interpret these bytes as cursor movement, color changes, or line rewrites, which lets an attacker overwrite prior log lines or fabricate entries that appear legitimate.

Attack Vector

An attacker with a low-privileged Kibana account submits crafted values through fields Kibana logs, such as search parameters, dashboard names, or authentication attempts. The injected payload contains ANSI escape codes that reposition the cursor or rewrite text. When an administrator views the log file with tools like cat, less -R, or tail, the terminal renders the attacker-controlled sequences. This can conceal malicious activity, spoof successful authentications, or misdirect incident response. See the Elastic Kibana Security Update for vendor-provided technical detail.

Detection Methods for CVE-2026-49091

Indicators of Compromise

Presence of non-printable byte sequences such as 0x1b[ (ANSI CSI introducer) inside Kibana log files under paths like /var/log/kibana/ or the configured logging.dest.
Log lines containing embedded \r or \n characters that visually rewrite adjacent records.
Requests to Kibana endpoints containing URL-encoded escape sequences (%1b, %0d, %0a) in query parameters, headers, or JSON bodies.

Detection Strategies

Scan Kibana log files for control characters using grep -P '[\\x00-\\x08\\x0b-\\x1f]' to identify tampered entries.
Correlate anomalous log rendering with recent low-privileged user activity to identify the injection source.
Alert on inbound HTTP requests to Kibana containing percent-encoded control bytes in user-supplied fields.

Monitoring Recommendations

Ship Kibana logs to a centralized platform that displays raw bytes rather than interpreting terminal escapes.
Baseline expected log formats and alert on deviations, including unexpected byte ranges or line-length anomalies.
Review audit trails for authentication and dashboard-management events during the exposure window.

How to Mitigate CVE-2026-49091

Immediate Actions Required

Upgrade Kibana to version 7.17.15, 8.11.1, or later per the Elastic advisory.
Restrict Kibana access to trusted users and enforce least-privilege role assignments until patching is complete.
Audit existing Kibana log files for embedded escape sequences and preserve copies for forensic review.

Patch Information

Elastic released fixed builds in Kibana 7.17.15 and 8.11.1. Details and upgrade guidance are available in the Elastic Kibana Security Update.

Workarounds

View Kibana logs only with tools that do not interpret escape sequences, such as cat -v or less without the -R flag.
Pipe log files through a sanitizer that strips control characters before display, for example tr -d '\000-\010\013-\037'.
Forward logs to a SIEM or log-viewing UI that renders raw text and does not execute terminal control codes.

bash

# Configuration example
# Safely inspect Kibana logs for injected control characters
grep -aP '[\\x00-\\x08\\x0b-\\x1f]' /var/log/kibana/kibana.log

# View logs with escape sequences neutralized
cat -v /var/log/kibana/kibana.log | less